THE 


PHOTOGRAPHIC  NEGATIVE, 


WRITTEN  AS 

A   PRACTICAL  GUIDE 

TO    THE    PREPARATION    OF    SENSITIVE    SURFACES    BY    THE 
CALOTYPE,  ALBUMEN,  COLLODION,  AND  GELATINE  PRO- 
CESSES, ON  GLASS  AND  PAPER,  WITH  SUPPLEMENT- 
ARY  CHAPTERS  ON    DEVELOPMENT,    ETC.,   ETC. 

3?  1 1 

BYTHE     iMA 

-•-1'1 

REV.    W.    H.    BURBANK, 

Author  of  Photographic   Printing  Methods,    etc.,    etc. 


NEW    YORK: 
SCOVILL  MANUFACTURING  COMPANY.    W.  IRVING  ADAMS,  Agent. 

1888. 


Entered,  according  to  Act  of  Congress,  in  the  year  1888,  by  the 

SCOVILL  MANUFACTURING  COMPANY, 
in  the  Office  of  the  Librarian  of  Congress.'at  Washington,  D.  C. 


-B 


CONTENTS. 


PREFACE 3 

CHAPTER  I. 

GENERAL  REMARKS  ON  SENSITIVE  SURFACES,  ETC 7 

CHAPTER  II. 
PRELIMINARY  REMARKS  ON  EXPOSURE,   DEVELOPMENT,  FIXING,  ETC.  . .  23 

CHAPTER  III. 
CALOTYPE 32 

CHAPTER  IV. 
SENSITIVE  SURFACES  ON  GLASS. — PREPARATION  OF  THE  GLASS 39 

CHAPTER  V. 
THE  ALBUMEN  PROCESS 44 

CHAPTER  VI. 
THE  OLD  COLLODION  PROCESS,  WET  PLATES 50 

CHAPTER  VII. 
THE  COLLODION  PROCESS,  DRY  PLATES 65 

CHAPTER  VIII. 
COLLODION  EMULSION. — COLLODIO-.BROMIDE  OF  SILVER .  73 

CHAPTER  IX. 
THE  GELATINE  PROCESS 86 

CHAPTER  X. 
COATING  THE   PLATES 110 

CHAPTER  XI 
DEVELOPMENT,  FIXING,  ETC 115 

CHAPTER  XII. 

PAPER   NEGATIVES.— STRIPPING  FILMS  ON    PAPER,    CARD-BOARD,  AND 
COLLODION 130- 


11  CONTENTS. 

PAGE 

CHAPTER  XIII. 
FAILURES  IN  THE  GELATINO- BROMIDE   PROCESS 147 

CHAPTER  XIV. 
METHODS  OF  STRIPPING  FILMS  FROM  GLASS   PLATES 151 

CHAPTER  XV. 
COLOR-SENSITIVE  PLATES 153 

CHAPTER  XVI. 
BLACK  AND  WHITE  NEGATIVES 160 

CHAPTER  XVII. 
INSTANTANEOUS  PHOTOGRAPHY 164 

CHAPTER  XVIII. 

TOUCHING-UP    THE   NEGATIVE 169 

CHAPTER  XIX. 
PHOTO- MICROGRAPHY 171 

CHAPTER  XX. 
MICRO-PHOTOGRAPHY 183 

CHAPTER  XXI. 
THE  TRANSFORMATION  OF  NEGATIVES  INTO  POSITIVES 186 

CHAPTER  XXII. 

OBERNETTER'S  METHOD  FOR  THE  DIRECT  PRODUCTION  OF  NEGATIVES 
FROM  NEGATIVES . .  .190 


INDEX 193 


PREFACE. 

THIS  book,  like  its  companion,  "Photographic  Printing 
Methods,"  is  the  outcome  of  my  wish  to  testify  to  the  exceed- 
ing great  interest  which  I  take  in  photography,  an  interest 
which  has  been  deepened  by  my  study  of  the  literature  of  the 
science  and  a  growing  knowledge  of  the  many  processes  to 
which  it  has  given  birth. 

Some  few  of  those  processes  I  endeavored  to  explain  in  my 
former  volume.  Others  of  equal  interest  I  have  selected  for 
description  in  the  following  pages. 

I  have  aimed  to  select  only  those  methods  known  to  have  a 
permanent  value. 

If  it  be  objected  that  some  of  them  no  longer  have  a  prac- 
tical value,  let  it  be  remembered  that  an  acquaintance  with 
them  is  necessary  to  a  thorough  knowledge  and  appreciation  of 
the  enormous  advance  which  photography  has  made  in  these 
later  years. 

It  is  folly  to  neglect  the  treasures  of  past  experience. 

There  is  a  culture,  a  completeness  of  knowledge,  in  this  as 
in  other  sciences. 

I  have  endeavored  to  make  this  knowledge  easy  of  attain- 
ment by  giving  a  few  typical  formulae  under  each  of  the  his- 
torical negative  processes. 

The  arrangement  of  the  chapters  follows  the  historical  or 
chronological  order  of  the  development  of  the  negative  proc- 
ess, from  the  calotype  of  Fox-Talbot  to  the  pellicular  film  of 
to-day. 

1  make  no  other  claim  to  originality  than  is  implied  in  the 
selection  and  arrangement  of  the  material  at  my  command. 
The  appended  list  of  authorities  bears  abundant  witness  to  my 
indebtedness  to  better  workers  in  the  same  field. 

I  have  sought  to  make  a  practical  book,  valuable  alike  to  the 
amateur  and  to  the  professional,  and  I  bespeak  for  my  effort 
the  kindly  criticism  which  well-meant  striving  always  merits. 


To  Dr.  Charles  Ehrmann  and  W.  I.  Lincoln  Adams,  of  the 
Photographic  Times,  my  thanks  are  due,  as  well  for  the 
warm  interest  which  they  have  shown  in  the  work,  as  for  the 
valuable  advice  and  assistance  they  have  freely  given. 

It  is  with  a  feeling  of  regret  that  I  bring  to  a  close  a  task 
which  has  been  full  of  pleasure  and  profit,  and  one  which  I 
trust  may  have  a  genuine,  though,  perhaps,  a  small  value  to 
my  brother  photographers,  to  whom  I  respectfully  dedicate 
my  work. 

R&v.  W.  H.  Burbank. 

NEWBUKG,  N.  Y.,  February,  1888. 


LIST  OF  PHOTOGRAPHIC  WORKS  CONSULTED. 

ABNEY,  CAPT.  W.  DE  W. — Photography  with  Emulsions.  Scovill  Mfg. 
Co.,  N.  Y.  1886. 

ABNEY,  CAPT.  W.  DE  W.— A  Treatise  on  Photography.  D.  Appleton  & 
Co.,  N.  Y.  1878. 

BOIVIN,   E.— Procede  au  Collodion  Sec.     Gauthier-Villars,  Paris.     1883. 

DAVANNE,  A.— La  Photographic.     Gauthier-Villars,  Paris.     1886. 

DAVID  and  SCOLIK.— Die  Photographic  mit  Brom-Silber  Gelatine.  Hart- 
leben,  Wien. 

EDER,  J.  M.— Modern  Dry  Plates.  E.  &  H.  T.  Anthony  &  Co.,  N.  Y. 
1881. 

HARDWICH,  REV.  T.  F. — A  Manual  of  Photographic  Chemistry.  Scovill 
Mfg.  Co.,  N.  Y.  1886. 

HUBERSON,  G. — Precis  de  Microphotographie.  Gauthier-Villars,  Paris. 
1879. 

LIESEGANG,  PAUL. — Die  Collodion-Verfahren.  Ed.  Liesegang.  Diissel- 
dorf. 

MALLMANN  and  SCOLIK. — Mittheilungen. 

MARTIN,  A. — Handbuch  der  Gesammten  Photographic.     Wien.     1854. 

PELEGRY,  ARSENE. — La  Photographic  des  Peintres,  des  Voyageurs,  et  des 
Touristes.  Gauthier-Villars,  Paris.  1885. 

PIERRE  PETIT  FILS,  A. — La  Photographic  Industrielle.  Gauthier-Villars, 
Paris.  1887. 

Roux,  V. — Traite  Pratique  de  la  Transformation  des  Negatives  en  Posi- 
tives. Gauthier-Villars,  Paris.  1881. 

TISSANDIER,  G. — A  History  and  Handbook  of  Photography.  Scovill 
Mfg.  Co.,  N.  Y.  1877. 

TRUTAT,  E. — Traite  Pratique  de  Photographic  sur  Papier  Negatif.  Gau- 
thier-Villars, Paris.  1884. 

VIALLANES,  H. — La  Photographic  Appliquee  aux  Etudes  d'Anatomie 
Microscopique.  Gauthier-Villars,  Paris.  1886. 

VOGEL,  H.  W.— Progress  in  Photography.  Edward  L.  Wilson,  Philadel- 
phia. 1883. 

VOGEL,  H.  W.— Handbook  of  the  Art  and  Practice  of  Photography. 
Benerman  &  Wilson,  Philadelphia.  .  1871. 

VOGEL,  H.  W. — Die  Photographic  Farbiger  Gegenstande.  Oppenheim, 
Berlin.  1885. 

WILSON,   E.   L.— Photographies.     E.  L.  Wilson,  Philadelphia.     1883. 

WILSOX,  E.  L. — Quarter  Century  in  Photography.  E.  L.  Wilson,  New 
York.  1887.  ~ 

Valuable  information  has  also  been  derived  from  the  British  Photo- 
graphic Annuals,  from  the  American  Annual  of  Photography  for  1887, 
and  from  the  columns  of  The  Photographic  Times  and  other  American  and 
foreign  photographic  journals. 


CHAPTER  I. 

GENERAL  REMARKS  ON  SENSITIVE  SURFACES,  ETC. 

IT  is  proposed  in  this  chapter  to  give  a  brief  statement  of 
the  nature  of  the  various  sensitive  compounds  in  most  com- 
mon use  in  photography,  followed  by  brief  notes  on  the  ma- 
nipulations common  to  all  negative  methods  described  in  sub- 
sequent chapters. 

Substances  Sensitive  to  Light. — The  number  of  substances 
which  are  sensitive  to  the  action  of  light  is  infinite.  There  is 
reason  to  believe  that  there  is  no  substance  which  is  not  more 
or  less  changed  in  outward  appearance  or  in  internal  struc- 
ture by  the  continued  action  of  light. 

But  while  this  is  true,  thus  far  but  three  compounds  have 
come  into  general  use  for  the  production  of  photographic 
negatives  ;  these  are  the  iodide,  the  bromide,  and  the  chloride 
of  silver ;  and  more  rarely,  the  fluoride  of  silver.  These  prod- 
ucts of  double  decomposition  are  very  far  from  possessing 
equal  value  in  negative  work. 

The  bromide  of  silver  is  the  one  of  the  three  compounds 
which  most  perfectly  meets  all  the  requirements  demanded  by 
the  varying  needs  of  the  photographer,  which  are  that  the 
result  due  to  the  action  of  light  shall  be  effected  as  speedily  as 
possible,  that  the  tone  values  of  different  colors  shall  be  repro- 
duced on  the  plate  as  they  are  on  the  retina,  and  that  the 
quantities  of  light  which  give  the  impression  of  high  lights, 
half-tones,  and  shadows  shall  produce  the  same  effect  on  the 
sensitive  surface  that  they  produce  on  the  human  eye. 

As  the  result  of  much  experiment  and  investigation,  it  has 
been  found  that  while  the  iodide  and  the  chloride  possess  one 
or  more  of  these  qualities  in  a  higher  degree  than  the  bromide, 
the  latter  is  superior  to  the  others  in  that  it  meets  fairly  well 


8  THE   PHOTOGRAPHIC  NEGATIVE. 

all  the  requirements.  It  is  more  sensitive,  and  gives  a  better 
rendering  to  half-tones  than  either  of  the  others.  For  certain 
purposes,  however,  the  iodide  or  the  chloride  may  be  advan- 
tageously substituted  for  the  bromide,  or  combined  with  it. 
For  the  reproduction  of  plans,  engravings,  designs,  etc.,  in 
line  work,  the  iodide  is  superior  to  either  of  the  others. 

The  chloride,  owing  to  its  comparative  slowness,  is  but  little 
used  in  negative  work,  but  is  invaluable  for  the  production  of 
positives  on  glass. 

The  fluoride  of  silver  has  been  recommended  by  Obernet- 
ter  and  Yogel  for  orthochromatic  plates. 

Many  formulae  are  based  on  the  combination  in  different 
proportions  of  the  iodide  and  bromide,  and,  less  often,  the 
chloride,  in  order  that  the  excellencies  of  one  may  counter- 
balance the  defects  of  the  others. 

No  difficulty  will  be  experienced  in  effecting  this  combina- 
tion if  care  be  taken  to  have  the  amount  of  silver  at  least  equal 
to  the  total  of  the  combining  weights  of  the  salts. 

The  necessity  for  this  is  based  on  the  law  of  chemical  affin- 
ity. The  iodides,  bromides,  and  chlorides  differ  in  the  order 
named  in  their  affinity  for  nitrate  of  silver.  If  a  solution  of 
nitrate  silver  be  added  gradually  to  a  solution  containing  an 
iodide,  a  bromide,  and  a  chloride,  the  iodide  of  silver  will  be 
formed  first ;  next,  the  bromide  of  silver  after  all  the  soluble 
iodide  has  been  converted,  and  after  the  conversion  of  the 
bromide,  the  chloride  is  fonned. 

So  powerful  is  the  law  of  affinity  governing  these  combina- 
tions, that  the  precipitates  formed  will  be  decomposed,  if 
necessary,  to  satisfy  it. 

If  sufficient  of  a  solution  of  chloride  of  sodium  has  been 
added  to  a  solution  of  nitrate  of  silver  to  convert  all  the 
nitrate  into  the  chloride,  the  latter  will  be  decomposed  and 
transformed  into  the  bromide  of  silver,  if  a  bromide  solution 
is  added,  which  in  turn  will  be  changed  into  the  iodide  of  sil- 
ver on  the  addition  of  an  iodide  solution. 

The  Film. — Owing  to  the  impossibility  of  spreading  the 
sensitive  salt  of  silver  formed  by  double  decomposition  when 
an  iodide,  a  bromide,  or  a  chloride  solution  is  poured  into  a 


GENERAL   REMARKS    ON   SENSITIVE    SURFACES,    ETC. 

solution  of  nitrate  of  silver,  directly  upon  the  glass,  and  of 
holding  it  there  during  all  the  manipulations  necessary  to  the 
production  of  the  finished  negative,  it  was  found  necessary  to 
incorporate  the  sensitive  salts  with  other  substances  capable  of 
giving  the  glass  support  a  regular,  continuous,  and  adhering 
surface. 

Many  important  considerations  govern  the  choice  of  these 
substances.  They  must  be  capable  of  liquefaction  in  order  that 
they  may  be  easily  and  quickly  spread  upon  the  glass  or  other 
support ;  they  must  have  the  property  of  setting,  or  hardening 
on  the  support ;  they  must  be  or  become  insoluble  in  the  suc- 
cessive baths  through  which  they  must  be  passed ;  they  must 
be  easily  permeated  by  the  various  reagents  to  whose  action 
they  will  be  submitted,  and  they  must  have  no  injurious  effect 
upon  the  sensitive  salts. 

The  result  of  patient  and  laborious  investigation  long- 
continued  has  narrowed  the  list  of  suitable  substances  down  to 
three :  albumen,  collodion,  and  gelatine,  given  here  in  the 
order  of  their  introduction.  Each  of  these  has  given  its  name 
to  a  group  of  processes,  the  best  of  which  will  be  described  in 
later  chapters. 

At  this  point  it  is  sufficient  to  say  that  each  of  these  sub- 
stances has  its  merits  and  its  defects.  Albumen  gives  films  to 
the  finest  grain,  but  of  great  tenuity.  It  must  be  coagulated 
by  a  strong  nitrate  bath,  which  lessens  its  permeability,  and 
thus  lengthens  the  time  of  exposure.  Collodion  films  set 
very  rapidly,  owing  to  the  evaporation  of  the  solvents ;  they 
are  easily  permeated  by  the  various  photographic  reagents ; 
they  are  easy  and  economical  of  production,  and  while  they  do 
not  always  unite  great  sensitiveness  with  good  keeping  quali- 
ties, they  unquestionably  yield  negatives  of  irreproachable  print- 
ing qualities,  superior  in  many  respects  to  those  produced  on 
the  modern  gelatine  plates. 

The  collodion  process  has  too  many  points  of  excellence  to 
be  finally  superseded  by  any  rival  methods,  although  at  present 
it  may  seem  to  be  in  abeyance,  owing  to  the  great  popularity 
enjoyed  by  gelatine  emulsion  plates.  Gelatine  gives  quickly- 
setting,  highly-sensitive  films,  which  retain  their  good  quali- 


10  THE   PHOTOGRAPHIC   NEGATIVE. 

ties  for  an  indefinite  period,  and  which  are  easily  acted  upon 
by  the  reagents,  and  notwithstanding  some  drawbacks,  gelatine 
has  usurped  the  place  once  held  by  collodion  in  the  photo- 
graphic laboratory. 

The  Dark-room  and  Laboratory. — The  convenience  and 
comfort  of  the  photographer  will  be  greatly  enhanced  by  the 
arrangement  of  the  room  or  rooms  in  which  his  work  is 
done.  The  dark-room  in  which  the  sensitive  surfaces  are 
prepared  and  developed  may  be  of  any  size  within  reach  of 
the  operator;  it  must  be  lighted  in  such  a  way  as  to 
enable  him  to  see  what  he  is  doing  without  the  light  ex- 
erting any  injurious  effect  upon  the  preparations.  Experi- 
ment has  shown  that  the  red  end  of  the  spectrum  has  least  in- 
fluence upon  iodide  and  bromide  of  silver ;  therefore  a  light 
varying  from  orange  to  red  or  ruby  is  in  common  use. 

It  must  be  borne  in  mind  that  no  light  is  absolutely  non- 
actinic,  that  is,  without  reducing  power  on  salts  of  silver  ;  the 
only  difference  between  rays  of  different  colors  being  the 
length  of  time  required  to  effect  the  reduction.  The  orange- 
red  end  of  the  spectrum  being  the  slowest  in  its  action,  some 
one  of  these  colors,  or  a  combination  of  them,  is  used  for  dark- 
room illumination. 

For  albumen,  collodion,  and  slow  gelatine  plates  yellow  light 
is  safe;  for  highly  sensitive  gelatine  plates  a  ruby  or  a  green- 
ish-yellow light  must  be  used,  and  the  plate  exposed  to  its  ac- 
tion as  little  as  possible.  For  orthochromatic  plates,  which  are 
made  highly  sensitive  to  the  yellow  and  red  rays,  the  smallest 
possible  amount  of  illumination  is  necessary,  and  the  plates 
must  be  most  carefully  guarded  from  the  direct  rays.  Schu- 
man,  Eder,  and  others  use  a  screen  made  of  three  thicknesses 
of  brown  tissue-paper.  This  gives  a  pleasant  and  safe  light, 
which  is  especially  recommended  for  color-sensitive  or  ortho- 
chromatic  plates. 

The  source  of  light  may  be  gas,  oil,  electricity,  or  the  sun, 
according  to  the  taste  of  the  operator ;  it  may  be  inside  or  out- 
side the  dark-room,  as  preferred.  My  own  preference  is  for 
an  oil  or  gas  light  outside  the  rooms.  An  opening  of  conven- 
ient size,  shape,  and  position  is  cut  in  one  of  the  walls  of  the 


GENERAL    REMARKS    ON    SENSITIVE    SURFACES,    ETC. 


11 


dark-room ;  this  is  provided  with  sliding  frames  carrying  re- 
spectively a  ground  glass,  a  yellow,  a  green,  and  a  ruby  glass  ; 
a  curtain  is  arranged  to  slide  back  and  forth  behind  these 
frames,  and  a  shade  is  hinged  to  the  wall  above.  This  com- 
bination of  arrangements  seems  to  give  all  the  necessary  modi- 
fications, and  the  changes  are  quickly  and  easily  made. 

The  size  and  internal  fittings  of  the  dark-room  will  vary  to 
suit  the  convenience  of  the  operator,  and  the  amount  and  kind 
of  work  to  be  done  in  it.  If  the  room  is  used  only  for  devel- 
opment it  need  not  be  larger  than  six  by  eight  feet.  If  it  is 
to  be  used  as  well  for  the  preparation  of  plates  it  must  neces- 
sarily be  larger  ;  nine  by  twelve  feet  will  be  a  convenient  size 
for  a  room  of  this  description. 

For  the  guidance  of  those  who  may  wish  to  fit  up  such  a 
room  the  following  diagram  and  description  is  given  : 


9ft. 


FIG.  1. 


A,  is  a  broad  shelf  at  which  the  coating  of  thejplates  is  done. 
On  it  is  the  levelled  slab  used  to  hasten  the  setting  of  gelatine 
plates,  and  above  are  shelves  containing  the  various  chemicals, 
vessels,  and  utensils  used  in  the  preparation  of  the  sensitive 
compounds.  B,  immediately  facing  the  window,  is  the  devel- 
oping shelf.  It  inclines  slightly  toward  the  sink  E,  and  is 
covered  with  sheet  lead.  Above  it  on  suitable  shelves  are 
stored  the  developing  solutions  and  chemicals.  The  space  un- 
derneath is  divided  into  vertical  compartments  to  hold  the 


12 


THE    PHOTOGRAPHIC    NEGATIVE. 


various  sized  trays  used  for  development.  C,  is  a  shelf  run- 
ning across  the  room.  The  end  nearest  the  sink  is  used  for 
fixing,  and  here  are  kept  all  fixing  solutions  and  trays.  D,  is 
the  drying-box,  and  F,  is  a  light-tight  closet  for  the  storage  of 
plates,  sensitive  paper,  etc. 

The  double  door  arrangement  shown  in  the  cut  is  a  great 
convenience,  allowing  ingress  or  egress  without  the  necessity 
of  covering  the  plates  to  prevent  them  from  being  light-struck. 

The  open  space  in  the  middle  of  the  room  is  large  enough 
to  be  utilized  for  enlarging  purposes.  The  wall  space  above 
and  below  the  shelves  shown  in  the  cut  may  be  fitted  up  to 
suit  special  needs.  The  room  is  ventilated  by  boring  holes  at 
the  top  and  bottom  of  one  side  and  covering  them  in  such  a 
way  as  to  prevent  the  ingress  of  light.  The  method  shown  in 
the  cut  below  is  simple  and  effective. 


JL 


J 


FIG.  2. 

Cleanliness  will  be  greatly  promoted  by  covering  the  floor 
with  oil  cloth ;  this  is  easily  cleaned  and  can  be  renewed  when 
worn  out. 

Such  a  room  as  this  would  seem  to  meet  all  the  requirements 
of  the  professional  or  amateur  photographer,  especially  if  a  good 
supply  of  running  water  can  be  laid  on.  In  default  of  this,  a 
large  tank  can  be  fastened  to  the  wall  above  the  sink  and  fitted 
with  a  tap. 

The  Drying-Box.  —  Many  photographic  processes,  both 
negative  and  positive,  require  a  place  in  which  the  sensitive 


GENERAL    REMARKS    ON    SENSITIVE    SURFACES,    ETC. 


13 


surfaces  can  be  dried  by  heat  or  otherwise,  and  in  which  they 
can  be  protected  from  light  and  dust. 


FIG.  3. 

The  drying-box  shown  in  Fig.  3  will  answer  all  these  needs, 
and  it  is  easy  of  construction  and  effective  in  operation.  It 
may  be  placed  in  the  dark-room,  if  the  coating  is  done  there, 
or  elsewhere,  to  suit  the  convenience  of  the  workman. 

It  is  impossible  to  give  any  very  definite  dimensions,  as 
these  vary  according  to  individual  needs.  A  convenient  size 
for  the  amateur  workman  is  three  feet  high,  two  feet  wide, 
and  one  foot  deep  from  back  to  front.  The  box  is  divided 
into  two  unequal  sized  compartments,  each  closed  by  a  door 
fitted  light-tight.  The  upper  portion,  which  occupies  about 
three-fourths  of  the  box,  is  the  drying  space  proper,  and  is 
fitted  as  shown  with  notched  side  pieces  to  allow  easy  displace- 
ment of  the  shelves.  The  bottom  is  a  moderately  thick  piece 
of  sheet  iron,  accurately  and  tightly  fitted  to  the  sides  of  the 
box,  to  prevent  the  escape  of  gas  into  the  drying  chamber.  In. 


14:  THE    PHOTOGRAPHIC    NEGATIVE. 

one  corner  of  this  plate  a  hole  is  cut  to  take  the  ventilating- 
pipe,  which  passes  through  the  back  and  is  there  again  bent 
at  right  angles.  A  second  pipe,  also  bent,  leading  from  the 
top  of  the  box,  serves  in  connection  with  the  first  to  establish 
a  current  of  air.  If  it  is  necessary  to  dry  the  sensitive  surfaces 
by  hot  air,  the  source  of  heat  is  placed  in  the  lower  compart- 
ment, immediately  under  the  iron  plate.  If  a  current  of  cold 
air  is  desired,  a  lamp  6r  gas  jet  is  placed  in  the  upper  pipe. 
When  not  in  use  as  a  drying-box,  it  can  be  used  for  other  pur- 
poses. Wood  may  be  used  in  its  construction  in  place  of 
metal,  but  the  danger  of  fire  is  increased. 

This  is  the  box  recommended  by  M.  Davanne,  who  also 
gives  the  following  method  for  drying  the  plates  vertically. 


FIG.  4. 

As  shown  by  the  cut,  Fig.  4,  the  racking  arrangement  con- 
sists of  three  bars  of  wood  placed  side  by  side  on  the  movable 
ledges  of  the  drying-box.  The  middle  bar,  which  is  one-quar- 
ter of  an  inch  thinner  than  the  two  side  bars,  is  provided  with 
a  series  of  vertical  rods  placed  about  four  inches  apart ;  they 
are  about  six  inches  high,  and  of  sufficient  size  to  prevent 
bending  or  shaking.  Between  these  bars  pieces  of  glass  rods, 
one-half  an  inch  high,  are  fixed.  With  this  arrangement  two 
plates  can  be  placed  between  the  rods.  If  it  is  preferred,  the 
glass  rods  can  be  dispensed  with,  and  the  wooden  uprights 
brought  nearer  together,  but  one  plate  can  then  be  placed 
against  each  upright.  The  side  bars  are  one-quarter  of  an  inch 
higher  than  the  middle  one.  Their  two  upper  surfaces  are 


GENERAL    REMARKS    ON    SENSITIVE    SURFACES,    ETC. 


15 


beveled  off,  and  glass  rods  are  fitted  into  grooves  cut  in  the 
tops  of  each.  The  plates  rest  on  these  rods,  which  are  easily 
cleaned  after  each  operation  of  drying. 

When  paper  coated  with  emulsion  is  to  be  dried  in  this  box, 
it  is  only  necessary  to  remove  the  middle  bar,  and  to  pin  the 
paper  to  the  two  side  bars. 


FIG.  5. 


-6                  6 

jl 

m                     i 

3                     i 

B 

-3                            E 

4i             i 

c        c 

^__D 

FIG.  6. 

©  ©  © 
l>  66 


WJ^ 


FIG.  7. 


FIG.  8. 


FIG 


Figures  5,  6,  7,  8,  and  9,  illustrate  the  details  of  the  con- 
struction of  a  more  elaborate  drying-box,  of  German  origin,  I 
believe.  Fig.  5,  is  a  general  plan  of  the  framework,  showing 
the  sliding  door.  Fig.  6,  shows  the  ventilating  arrangements 
from  the  front ;  Fig.  7,  is  a  side  view ;  Fig.  8,  the  bottom  plan, 
and  Fig.  9  the  cut-off  for  excluding  light  from  the  interior. 
Dust  is  excluded  by  a  strip  of  muslin  glued  over  the  opening 
of  the  cut-off. 

D,  Figures  6,  7,  and  8,  is  a  sheet-iron  box,  six  inches  deep, 
fastened  to  the  bottom  of  the  drying-box,  projecting  far 


16  THE   PHOTOGRAPHIC   NEGATIVE. 

enough  beyond  the  back,  to  allow  the  insertion  of  the  six-inch 
pipe,  E,  Figures  6,  7,  and  8.  On  the  inside  are  riveted  two 
pieces  of  sheet  iron,  four  and  one-half  inches  wide,  and  passing 
completely  across.  C,  C,  Figures  6,  7,  and  8,  are  pieces  of  two- 
inch  iron  pipe,  four  inches  long,  projecting  into  the  box,  D, 
and  opening  into  the  drying  chamber,  F.  Figure  7,  is  a  gas 
jet,  which,  burning  inside  the  pipe,  E,  produces  the  current. 
K,  Figure  7,  is  a  door  in  the  pipe,  which  allows  the  height  of 
the  flame  to  be  seen.  In  default  of  gas,  an  oil  lamp  can  be 
used,  supporting  it  on  angle-irons  riveted  inside  the  pipe. 
The  shelving  arrangements  can  be  made  to  suit  the  fancy  of 
the  operator.  Tbe  framework  is  of  wood,  the  sides  may  be  of 
wood,  sheet  iron,  or  zinc,  as  desired. 

If  the  coating-room  is  dry,  well  ventilated,  free  from  dust, 
and  light-tight,  the  plates  may  be  racked  away  on  shelves 
placed  near  the  top  of  the  room  to  dry  spontaneously.  This 
is  my  own  practice,  and  I  prefer  it  to  the  most  elaborate  dry- 
ing-boxes, which  do  not  always  dry  well. 

Utensils. — It  is  manifestly  impossible  to  give  a  complete  in- 
ventory of  all  the  various  glasses,  graduates,  and  other  para- 
phernalia which  accumulate  in  and  about  the  photographic 
work- shop.  Some  pride  themselves  on  doing  all  their  work 
with  the  fewest  possible  conveniences ;  while  others  must  have 
an  infinite  number  of  belongings  before  setting  to  work.  The 
list  which  is  here  given  is  intended  to  cover  everything  really 
needed  in  the  performance  of  all  the  processes  included  in 
these  pages.  If  the  list  seems  a  long  one  it  must  be  re- 
membered that  the  number  of  negative  processes  is  large, 
and  that  all  of  them  have  special  requirements  in  the  way  of 
apparatus. 

For  development  a  number  of  flat  trays  of  different  sizes 
will  be  needed.  These  may  be  of  glass,  porcelain,  gutta 
percha,  japanned  iron,  wood,  or  even  pasteboard  in  an  emer- 
gency. Glass  and  porcelain  are  the  cleanliest,  and  must  have 
the  preference  for  regular  work  in  the  dark-room. 

For  the  chemicals  nothing  can  be  better  than  the  wide- 
mouthed  glass-stoppered  bottles  used  by  druggists. 

For  mixing  solutions  the  cylindrical  glasses  known  as  beak- 


GENERAL   REMARKS    ON    SENSITIVE    SURFACES,    ETC. 


17 


ers  are  well  adapted,  and  a  number  of  these  of  different 
capacities  should  be  provided,  together  with  a  goodly  number 
of  glass  stirring-rods.  Graduates  of  different  sizes  are  a 
necessity;  test  tubes,  pipettes,  porcelain  capsules  for  heating 
liquids,  a  glass  mortar  and  pestle,  specific  gravity  glasses  for  de- 
termining the  specific  gravity  of  liquids,  glass  funnels  of  various 
sizes,  Bohemian  glasses  of  various  shapes  and  sizes  for  emulsion 
making,  a  retort  stand,  a  Bunsen  gas  burner,  or  a  Liebig  spirit 
lamp,  a  retort  or  two,  a  hot-water  bath,  two  or  three  drying 
racks,  a  washing  box,  a  distilling  arrangement,  and  an  apparatus 
for  hot  filtration  will  well  stock  the  photographic  laboratory. 
Not  all  of  them  need  be  kept  in  the  dark-room.  Most  of  them 
should  be  kept  in  a  room  set  apart  for  such  operations  as  do 
not  shun  the  light  of  day  ;  a  working  laboratory  in  fact,  which 
may  be  fitted  up  to  suit  the  inclination  and  purse  of  the  ex- 
perimenter. It  should  have  a  sink,  an  abundant  supply  of 
water,  a  strong  work  table,  with  a  stone  or  marble  top,  and  a 
draining  rack  where  the  various  glass  bottles,  etc.,  may  be  put 


FIG.  10. 

to  drain  and  dry  after  washing.  Such  a  rack  is  shown  in  Fig. 
10,  and  its  use  is  sufficiently  apparent  to  need  no  further  de- 
scription. 


18  THE    PHOTOGRAPHIC    NEGATIVE. 

Solutions. — The  photographer  uses  all  his  chemicals  in  the 
form  of  solutions.  The-  most  common  method  of  making  a 
solution  is  to  weigh  out  the  proper  amount  of  the  chemical 
required,  throw  it  into  the  bottom  of  a  bottle,  add  the  proper 
quantity  of  water,  and  then  leave  it  to  take  care  of  itself. 
This  is  the  simplest  method  and  the  poorest.  It  produces  a 
local  saturation  of  the  lower  portion  of  the  liquid,  and  in  a 
short  time  the  process  of  solution  ceases  entirely.  A  better 
way  is  to  pulverize  the  chemical  before  adding  the  water,  and 
to  assist  the  solvent  action  by  frequent  stirrings.  The  best 
way  is  to  keep  the  chemical  near  the  surface  of  the  liquid,  or 
even  above  it.  This  hastens  solution,  because  the  liquid  in 
contact  with  the  chemical  is  continually  being  replaced  as  the 
heavier  saturated  portion  falls  to  the  bottom.  Two  methods 
may  be  adopted  to  effect  this  result ;  one  is  to  pour  the  liquid 
into  a  wide-mouthed  bottle  and  to  suspend  the  chemical  in  a 
bag,  so  that  it  is  just  covered  ;  another  way,  and  the  more 
scientific,  is  shown  in  Fig.  11.  A  gutta-percha 
tube  fitting  tightly  into  the  mouth  of  a  flask  is 
forced  tightly  over  the  tube  of  a  funnel  to  pro- 
duce an  air-tight  joint.  Two-thirds  of  the  liquid 
is  poured  into  the  flask,  the  remaining  third  and 
the  chemical  to  be  dissolved  are  placed  in  the 
funnel  and  the  mouth  of  the  flask  is  hermetically 
sealed  by  forcing  the  rubber  tube  into  it.  The 
lower  end  of  the  tube  must  be  below  the  surface 
of  the  liquid.  As  the  air  cannot  escape,  and  the 
heavier  saturated  liquid  must  descend,  two  cur- 
rents are  soon  established  in  the  tube,  one  de- 
scending, bearing  the  saturated  liquid,  the  other 
ascending,  bearing  fresh  portions.  The  operation 
is  automatic  and  speedy.  If  the  filtered  solution 
is  wanted  it  is  only  necessary  to  place  a  filter 
paper  in  the  funnel.  A  saturated  solution  is 
FIG.  11.  made  by  placing  in  the  funnel  an  excess  of  the 
substance  to  be  dissolved. 

Filtration. — To  produce   clean   work   in   photography   all 
solutions  must  be  filtered.     The  means  of  doing  this  with  or- 


GENERAL    REMARKS    ON    SENSITIVE    SURFACES,    ETC. 


19 


dinary  aqueous  solutions  are  too  well  known  to  need  descrip- 
tion. Solutions  containing  gelatine,  gum,  and  similar  sub- 
stances, as  a  rule  need  to 
be  kept  warm  during  fil- 
tration to  prevent  them 
from  cooling  down  and 
filling  the  pores  of  the 
paper.  Two  very  effect- 
ive systems  of  warm  fil- 
tration are  shown  in  Figs. 
12  and  13.  In  both  the 
inner  glass  funnel  is  tight- 
ly fitted  to  the  outer  one 
of  tin  by  means  of  a 
pierced  cork.  Warm 
water  is  poured  into  the 
outer  funnel  and  its  tem- 
perature maintained  by  a 
spirit,  gas,  or  oil  lamp. 
Upward  filtration  will 

FIG   12. 

be  found  a  valuable 
method  for  filtering 
emulsions  of  any 
kind,  as  bubbles  are 
entirely  prevented. 
One  or  more  thick- 
nesses of  muslin,  ac- 
cording to  its  fineness, 
are  tied  over  the 
mouth  of  a  beaker  or 
other  glass,  the  bot- 
tom of  which  has  been , 
removed.  The  emul- 
sion is  placed  in  a  ves- 
sel a  trifle  larger  than  the  filter,  which  is  allowed  to  sink  by 
its  own  weight.  When  full  it  is  withdrawn  and  the  emul- 


20  THE    PHOTOGRAPHIC   NEGATIVE. 

eion  poured  out.     The  dish  containing  the  emulsion  should  be 
placed  in  a  hot  water  bath. 

In  case  of  need  the  ordinary  filter  paper  may  be  replaced 
with  glass,  as  in  the  case  of  strong  acid  or  alkaline  solutions, 
which  might  attack  the  paper,  or  with  filtering  cotton,  or  a 
piece  of  chamois  skin  previously  well  soaked  in  a  sal  soda  solu- 
tion and  well  washed  for  collodion  or  gelatine  emulsion. 
Flaxen  tow  is  also  sometimes  used  for  this  purpose. 

Precipitation. — The  term  precipitates  is  applied  to  the  in- 
soluble substances  which  are  formed  in  a  solution,  when  by  a 
change  in  the  nature  of  the  substance  held  in  solution  or  in 
the  solvent,  insoluble  and  non-crystalline  bodies  are  formed. 
Precipitation  is  resorted  to  to  obtain  certain  substances  or  fluids 
difficult  or  impossible  to  be  had  in  any  other  way.  The  liquid 
and  the  precipitate  are  first  separated  by  filtration,  and  then 
the  precipitate,  if  wanted,  is  freed  from  impurities  by  washing. 
Washing  Precipitates. — Precipitates  are  commonly  washed 
on  filter  paper,  small  quantities  of  water  being  poured  into 
the  filter  until  the  drainings  when  treated  with  the  proper 
reagents,show  no  traces  of  the  dissolved  substances  from  which 
the  precipitate  has  been  formed. 

Another  method  is  to  use  the  washing 
bottle  of  the  chemist,  shown  in  Fig.  1 4. 

A,  and  B,  are  two  glass  tubes  bent  as 
shown,  and  tightly  fitted  into  the  cork 
which  closes  the  mouth  of  the  bottle. 
The  precipitate  is  placed  in  the  bottle, 
which  is  then  partly  filled  with  water ; 
the  cork  is  then  inserted,  and  by  blow- 
ing through  B,  a  stream  of  water  is 
forced  through  A,  the  upper  end  of 
which  is  drawn  out  somewhat  to  diminish 
the  size  of  the  bore. 

Decantation. — When  the  precipitates  are  coarse  grained 
and  heavy  they  may  be  easily  and  quickly  washed  by  decanta- 
tion.  The  precipitate  is  placed  in  a  large  beaker  or  tumbler, 
which  is  then  filled  with  water,  and  the  contents  well  stirred 
with  a  glass  rod.  As  soon  as  the  precipitate  has  fallen  to  the 


GENERAL    REMARKS    ON   SENSITIVE    SURFACES,    ETC. 


21 


bottom  the  water  is  carefully  poured  off  as  closely  as  possible. 
This  operation  is  repeated  ten  or  more  times,  and  the  precipi- 
tate is  then  thrown  on  a  filter  and  allowed  to  drain. 

The  use  of  a  decantation  flask  will  greatly  facilitate  the 
operation.  This  is  a  flask  provided  with  two  tubes,  a  large 
and  a  small  one.  A  piece  of  fine  muslin  is  tied  over  the 
mouth  of  the  smaller  tube,  the  water  and  the  precipitate  are 
introduced  through  the  larger.  The  water  is  poured  away 
through  the  smaller  tube. 

Distilling  Apparatus.  —  Many  photographic  operations  re- 
quire distilled  water  to  secure  the  best  results;  it  would  be 
well  to  use  nothing  else  in  making  up  solutions.  The  use  of 
distilled  water  would  probably  be  more  general  were  it  not  for 
the  high  price  and  great  bulk  of  the  ordinary  worm  still. 
Pig.  15  illustrates  a  simple  form  of  a  portable  still  which  is 
open  to  neither  of  these  objections.  It  can  be  easily  and 
cheaply  constructed  by  any  tinman  ;  it  is  effective  in  operation 
and  easily  kept  clean.  The  dimensions  given  below  will  give 
a  still  capable  of  distilling  a  gallon  of  water  at  a  time.  It  is 
made  of  stout  tin  or  copper,  as  preferred.  The  cylindrical 


FIG.  15. 


body,  A,  is  thirteen  inches  high  and  seven  inches  in  diameter. 
The  funnel-shaped  lid,  B,  is  eight  and  a  half  inches  in  diam- 
eter and  five  inches  in  height  from  base  to  apex.  It  is  pro- 
vided with  a  flange,  0,  C,  to  fit  accurately  inside  the  cylinder 


22  THE    PHOTOGRAPHIC    NEGATIVE. 

like  an  ordinary  pail  cover,  and  a  tube,  D,  a  couple  of  inches 
long,  near  the  top  of  the  cone.  About  five  inches  from  the 
top  of  the  body  a  tube,  E,  about  ten  inches  long,  is  passed 
through,  terminating  at  the  inside  in  a  small  funnel,  F,  exactly 
under  the  tip  of  the  cone.  The  other  end  projects  about  three 
inches  at  the  outside  of  the  cylinder.  The  three  legs,  made  of 
strap  iron,  are  riveted  to  the  body,  and  may  be  of  any  conven- 
ient length. 

Common  tap  water  is  poured  into  the  cylinder,  the  cone  lid 
is  put  in  place,  and  the  apparatus  is  placed  over  a  gas  or  oil 
stove  near  the  water  supply.  A  gentle  stream  of  running 
water  is  led  into  the  cone  by  a  piece  of  rubber  tubing.  The 
steam  produced  from  the  boiling  water  is  condensed  on  the 
under  side  of  the  cone,  and  runs  down  into  the  funnel  and 
tube,  and  is  caught  in  a  flask  placed  underneath  the  pipe. 
This  still  is  the  invention  of  Mr.  C.  C.  Vevers,  of  England, 
the  description  being  given  nearly  in  his  own  words. 

If  running  water  cannot  be  had  the  cone  can  be  occa- 
sionally replenished  with  cold  water  from  a  pail,  or  small 
lumps  of  ice  can  be  thrown  in  now  and  then  to  keep  the  water 
cool. 


CHAFTEE  II. 

PRELIMINARY   REMARKS  ON   EXPOSURE,   DEVELOPMENT,  FIXING,  ETC. 

IT  will  serve  to  pave  the  way  to  the  more  practical  discus- 
sion of  the  manipulations  peculiar  to  the  different  negative 
processes  if  a  few  pages  are  devoted  to  the  general  principles 
common  to  all. 

The  production  of  a  negative  by  any  of  the  methods,  de- 
scribed later,  requires  an  exposure  to  light  more  or  less  pro- 
longed, followed  by  development,  fixing,  washing,  and  in 
many  cases  a  strengthening  or  weakening  of  the  image  pro- 
duced by  development.  While  each  of  these  manipulations 
has  special  modifications  to  adapt  it  to  the  different  pro- 
cesses, they  all  agree  in  certain  broad  and  general  principles,  - 
the  knowledge  of  which  is  essential  to  that  complete  mastery 
of  the  subject  without  which  the  operator  will  be  continually 
working  in  the  dark. 

These  general  principles  will  be  discussed  in  this  chapter, 
leaving  their  application  to  special  cases  to  be  explained 
later  on. 

Exposure. — Whenever  a  ray  of  light  falls  upon  a  sensitive 
surface  a  change  of  some  kind  is  produced.  Of  the  precise 
nature  of  this  change  we,  at  present,  know  but  very  little,  and 
where  little  is  known,  little  had  best  be  said.  We  do  know,  how- 
ever, that  this  change,  invisible  to  the  eye,  can  be  made  visible 
by  the  application  of  certain  reagents  to  the  exposed  surface. 
The  latent  image  then  shows  itself  with  a  perfection  and  de- 
tail proportioned  to  the  duration  of  the  exposure  and  the 
strength  of  the  reagent.  The  behavior  of  the  exposed  surface 
in  the  developer  is  to  some  extent  a  means  of  determining  the 
correctness  of  the  exposure.  If  the  image  appears  suddenly 
in  #11  its  details  and  then  as  suddenly  clouds  over,  we  know 


24:  -THE-   PHOTOGRAPHIC    NEGATIVE. 

the  exposure  was  too  prolonged.  If  the  image  comes  up  slow- 
ly and  is  poor  in  detail,  the  exposure  was  not  sufficient.  In 
neither  of  these  cases  will  a  geod  negative  be  produced. 

A  good  printing  negative  is  one  in  which  the  high  lights 
show  points  of  opacity,  and  the  deepest  shadows  almost  bare 
glass,  with  an  infinite  gradation  of  tones  between  these  two 
extremes.  Such  a  negative  is  largely  the  product  of  correct 
exposure.  Much  may  be  done  in  development  to  make 
amends  for  a  faulty  exposure,  but  the  best  technical  negative 
will  always  be  the  properly  exposed  and  rightly  developed 
one. 

Beyond  question  the  time  of  exposure  is  one  of  the  most 
important  of  photographic  manipulations,  and  even  with  a 
careful  study  of  all  the  facts  which  determine  its  length, 
aided  by  much  experience,  it  is  only  possible  to  acquire  an 
approximately  correct  judgment. 

Three  different  sets  of  facts  must  be  considered  in  this  con- 
nection ;  viz.,  the  physical,  chemical,  and  optical  conditions 
present  and  influencing  the  duration  of  the  exposure. 

The  physical  conditions  are  such  as  the  following:  the 
nature,  intensity,  and  color  of  the  light,  and  the  distance, 
color,  and  lighting  of  the  object  to  be  reproduced.  These 
the  view  photographer  has  little  or  no  power  to  change.  He 
must  take  them  as  he  finds  them,  and  rely  on  his  own  judg- 
ment as  to  the  time  of  exposure  best  suited  to  the  view  before 
him. 

Despite  many  ingenious  attempts,  no  mechanical  means  of 
settling  the  question  have  as  yet  been  discovered  of  sufficient 
accuracy  to  take  the  place  of  long  experience  and  good  judg- 
ment. The  simplest  are  based  on  the  darkening  action  of 
light  on  sensitive  paper  confined  in  a  box  and  exposed  through 
a  narrow  slit  cut  in  its  cover.  The  best  and  most  accurate 
require  too  much  scientific  knowledge  to  be  generally  useful, 
and  none  give  anything  more  than  a  relative  estimate  of  the 
intensity  of  the  light. 

The  chemical  conditions  depend  on  the  method  employed 
in  making  the  sensitive  compound;  sensitiveness  increasing  in 
the  following  order :  albumen,  calotype,  collodio-albumen, 


PRELIMINARY    REMARKS    ON    EXPOSURE,    ETC.  25 

dry  collodion,  wet  collodion,  gelatino-bromide.  The  compar- 
ative rapidity  of  each  is  approximately  given  in  the  following 
table  : 

Albumen 10  to  30  minutes 

Calotype 8  to  20  minutes 

Collodio-Albumen 3  to  10  minutes 

Dry  Collodion - 1  to    5  minutes 

Wet  Collodion 5  to  60  seconds 

Gelatino-Bromide 1  to  10  seconds 

These  figures  represent  average  results  with  emulsions  or 
preparations  of  medium  sensitiveness  in  each  class. 

The  optical  conditions  influencing  the  exposure  are  the 
focal  length  of  the  objective,  the  size  of  the  diaphragm,  the 
number,  thickness,  and  degree  of  coloration  of  the  lenses,  and 
the  distance  from  the  view. 

These  conditions  are  subject  to  one  or  more  of  the  following 


1.  The  time  of  exposure  varies  directly  as  the  focal  lengths 
of  the  objectives. 

2.  The  time  of  exposure  is  inversely  proportioned  to  the 
squares  of  the  diameters  of  the  diaphragms. 

3.  The  time  of  exposure  varies  inversely  as  the  distances  of 
the  objects  to  be  photographed.     To  this  law  is  due  the  repro- 
duction of  the  effect  known  as  aerial  perspective. 

Development. — To  the  eye,  and  even  to  the  microscope,  an 
exposed  plate  shows  nothing  to  distinguish  it  from  an  unex- 
posed  •  one.  The  developer  alone  detects  the  difference,  with- 
out, however,  conveying  any  information  as  to  the  nature  of 
the  change. 

Notwithstanding  much  patient  investigation  the  question  of 
the  nature  of  the  latent  image  is  still  an  unsettled  one.  The 
most  commonly  accepted  theory  is  that  a  molecular  change  is 
produced  by  the  action  of  light  upon  sensitive  compounds,  the 
molecules  being  pulled  apart,  as  it  were,  and  so  made  less 
stable. 

This  molecular  change  is  not  supposed  to  produce  any  sep- 
aration of  elements,  such  as  occurs  when  a  visible  image  is 
formed  by  the  action  of  light. 


26  THE    PHOTOGRAPHIC    NEGATIVE. 

The  function  of  a  developer  is  to  make  this  change  visible 
by  reducing  the  silver  in  those  parts  acted  upon  by  light  to  the 
metallic  state. 

It  has  long  been  a  disputed  question  among  photographic 
savants  whether  the  change  produced  in  a  sensitive  com- 
pound of  silver  is  a  physical  or  a  chemical  change.  With- 
out burdening  the  reader  with  the  arguments  advanced  in  sup- 
port of  each  of  these  positions,  it  may  be  stated  that  at  present 
the  weight  of  authority  seems  to  be  on  the  side  of  a  chemical 
change. 

It  may  be  regarded  as  a  tolerably  certain  fact  that  under  the 
action  of  light  the  haloid  salts  of  silver,  that  is,  the  bromide, 
iodide  and  chloride,  have  a  tendency,  more  or  less  powerful,  to 
return  to  the  metallic  state;  a  tendency  which  is  promoted  and 
made  permanent  by  the  action  of  developers,  which  are  al- 
ways reducing  agents ;  that  is,  they  are  substances  which  are 
able  to  reduce  the  soluble  salts  of  silver  to  the  metallic  state. 
We  may  thus  take  it  for  granted,  for  the  present  at  least,  that 
the  change  of  condition  produced  in  the  sensitive  compounds 
employed  for  the  production  of  negatives  is  a  chemical,  not  a 
physical  reaction. 

The  development  of  negatives  may  be  eifected  in  one  of  two 
ways: 

1st  Method. — The  new  compound  may  possess  an  attractive 
force.  The  action  of  light  on  sensitive  compounds  of  silver 
tends  to  cause  the  formation  of  a  substance  capable  of  attract- 
ing the  metal  of  which  it  is  a  salt,  when  slowly  deposited  from 
a  solution.  This  first  deposit  is  capable  of  attracting  more  of 
the  metal,  and  in  this  way  an  image  is  gradually  built  up. 
This  is  the  theory  of  the  physical  development  of  wet  collodion 
plates. 

2d  Method. — The  image  may  be  the  result  of  the  reduction,, 
more  or  less  complete,  to  a  more  elementary  state,  of  the  altered 
compound  when  treated  with  certain  solutions;  in  which  state 
it  may  have  the  same  attractive  power  as  before.  This  is  the 
rationale  of  all  alkaline  development. 

The  proper  development  of  a  negative  is  an  art  acquired 
only  after  long  experience  and  many  failures.  It  cannot  be 


PRELIMINARY    REMARKS    ON    EXPOSURE,    ETC.  27 

learned  from  books ;  it  must  be  acquired  at  the  developing 
table.  The  problem  to  be  solved  is  to  bring  forth  on  the  ex- 
posed surface  a  reproduction  of  the  original  which  shall  pre- 
serve all  the  varied  tones,  and  be  capable  of  reproducing  in  the 
print  the  impression  made  by  the  original. 

As  a  first  step  towards  the  solution  of  this  problem  it  is 
best  to  begin  with  a  weak  developer,  strengthening  it1  as  need 
arises.  This  gives  more  control  of  the  reducing  action  by 
which  the  image  is  built  up,  and  gives  the  operator  time  to  see 
and  meet  the  needs  of  each  case.  This  method  is  particularly 
desirable  with  instantaneous  exposures.  Here  a  strong  devel- 
oper would  probably  ruin  the  plate,  burying  the  high  lights  be- 
neath an  opaque  deposit  of  metallic  silver  long  before  any  detail 
was  visible  in  the  shadows.  It  is  always  best  to  make  sure  of 
the  details  before  securing  density.  The  latter  is  always  possible 
at  any  stage  of  development,  while  if  the  proper  degree  of 
density  is  reached  before  the  details  are  well  out,  the  plate  will 
be  lacking  in  that  exquisite  gradation  of  tone  which  makes  the 
charm  of  a  perfect  negative. 

The  common  practice  is  to  keep  the  developer  in  constant 
motion,  in  order  to  renew  the  portion  in  contact  with  the  plate, 
and  so  secure  uniformity  of  action. 

Many  operators,  however,  claim  that  finer  details  are  secured 
by  allowing  the  plate  to  remain  undisturbed.  In  the  case  of 
pyro  development  there  is  less  danger  of  the  film  becoming 
stained  by  the  oxidization  of  the  pyro. 

When  prolonged  development  is  necessary,  it  is  best  to  turn 
the  plate  face  down  in  the  developer,  supporting  it  by  the 
extreme  edges  in  such  a  way  as  to  leave  a  fair  depth  of  the 
solution  between  the  plate  and  the  bottom  of  the  tray. 

When  the  development  is  very  rapid,  as  with  wet  collodion 
plates  developed  with  protosulphate  of  iron,  the  plate  is  to  be 
held  in  the  hand  and  as  much  developer  as  the  plate  will  hold 
poured  on  and  allowed  to  act  until  the  process  of  develop- 
ment is  completed. 

If  the  latent  image  flashes  up  at  once  under  the  action  of 
the  developer,  the  exposure  was  too  great.  If,  however,  the 
high-lights  only  appear,  the  half-tones  hanging  back,  the  ex- 


28  THE    PHOTOGRAPHIC    NEGATIVE. 

posure  was  too  short.  Both  of  these  errors  can  be  corrected, 
to  a  certain  extent,  by  certain  modifications  of  the  developer. 

Development  must  be  continued  until  the  proper  degree  of 
density  is  reached,  generally  until  the  image  is  faintly  visible 
at  the  back  of  the  plate.  Viewed  by  transmitted  light  the 
highest  lights  should  be  nearly  opaque,  and  the  gradations  be- 
tween the  shadows,  the  half-tones,  and  the  high-lights  should 
be  well  marked  and  distinct. 

After  development,  the  plate  is  washed  in  several  changes 
of  water  and  then  fixed. 

Fixing. — The  office  of  the  fixing-bath  is  to  dissolve  out  all 
the  silver  salts  not  converted  to  the  metallic  state  by  the  devel- 
oper. If  this  were  not  done,  and  the  unfixed  plate  were  exposed 
to  the  action  of  light,  the  surface  of  the  plate  would  assume  a 
uniformly  dark  tint  and  the  image  would  be  lost. 

There  are  many  substances  which  possess  this  power  of  dis- 
solving the  salts  of  silver,  but  only  three  of  them  are  of  use  in 
photography;  these  are  the  alkaline  sulphocyanides  (potassi- 
um or  ammonium),  the  cyanide  of  potassium  and  the  thio- 
sulphate  of  soda,  commonly  known  as  hyposulphite  of  sodium. 
The  chemical  action  of  all  these  compounds  is  practically  the 
same.  In  conjunction  with  the  salts  of  silver  they  form  re- 
spectively the  sulphocyanide,  the  cyanide,  and  the  hyposul- 
phite of  silver,  all  of  which  are  insoluble  in  water,  but  soluble 
in  an  excess  of  alkaline  sulphocyanide,  cyanide,  or  hyposul- 
phite. Hence  the  necessity  of  employing  an  excess  of  the  fix- 
ing agent. 

The  sulphocyanide  and  the  cyanide  fixing-baths  are  but 
little  used ;  the  former  on  account  of  its  cost,  the  latter  be- 
cause of  its  exceedingly  poisonous  nature. 

Hyposulphite  of  soda  is  cheap,  harmless,  and  effective  ;  its 
sole  drawback  being  the  difficulty  of  eliminating  it  entirely 
from  the  negative,  without  which  perfect  elimination  the  keep- 
ing qualities  of  the  negative  are  greatly  lessened. 

The  effect  of  the  fixing-bath  is  to  deprive  the  negative  of 
its  milky  appearance  due  to  the  unreduced  silver.  This  it 
does  by  dissolving  the  unreduced  salts,  but  in  so  doing  the  ex- 
ceedingly unstable  compound  known  as  hyposulphite  of  silver 


PRELIMINARY    REMARKS   ON    EXPOSURE,    ETC.  29 

is  formed.  This  is  a  white  substance  which  rapidly  decom- 
poses into  black  sulphide  of  silver.  The  decomposition  does 
not  take  place  in  an  excess  of  hyposulphite  of  soda ;  in  this 
case  double  salts  are  formed  and  rapidly  dissolved.  The  quan- 
tity of  the  hypo  must  then  be  in  excess  of  the  amount  actually 
required  to  dissolve  the  unreduced  salt. 

The  fixing  action  is  commonly  supposed  to  be  complete 
when  the  negative  has  lost  its  milky  appearance.  Portions  of 
the  double  salts  may  still  be  undissolved,  however,  and  it  is 
best  to  allow  the  fixing  agent  to  act  for  a  few  moments  after 
the  milky  appearance  has  disappeared.  The  negative  is  then 
ready  for  washing. 

Washing. — Hyposulphite  of  soda  has  a  strong  inclination  to 
remain  in  the  pores  of  the  film,  especially  gelatine  films. 
These  require  a  thorough  washing  and  a  subsequent  treatment 
with  some  hypo  eliminator  to  eliminate  the  last  traces  of  the 
salt. 

The  negative  may  be  washed  in  ordinary  trays  in  running 
water,  or  by  frequently  changing  it,  but  this  method  requires 
longer  washing,  as  the  negative  lies  in  the  bottom  of  the  tray 
with  its  face  up,  upon  which  the  heavy  hypo-charged  liquid 
rests.  Another  method  is  to  place  the  negatives  in  washing 
boxes  provided  with  grooves,  and  then  wash  in  running  water. 
The  most  effective  method  is  to  place  the  negatives  film  side 
down  in  a  triangular  box  provided  with  a  stop  cock  at  one 
end,  and  to  wash  in  running  water  or  with  frequent  changes. 
The  hypo  as  it  leaves  the  film  falls  to  the  bottom  of  the  tray 
and  is  drawn  off  through  the  stop  cock.  Negatives  washed 
for  twenty  minutes  in  running  water  in  this  box  show  no 
traces  of  hypo  even  to  the  most  delicate  tests. 

Whatever  method  of  washing  is  adopted  it  is  always  safe  to 
test  for  hypo,  which  may  be  done  in  several  ways,  as  shown 
later  on.  After  sufficient  washing,  the  negatives,  if  on  gelatine 
films,  may  be  soaked  for  a  short  time  in  a  strong  alum  bath 
to  harden  the  film.  They  are  then  washed  a  few  moments 
longer,  and  after  the  faces  have  been  brushed  over  with  a 
broad  carnePs-hair  brush  to  remove  all  adhering  particles, 
they  are  racked  away  to  dry  in  a  place  free  from  dust. 


30  THE    PHOTOGRAPHIC    NEGATIVE. 

When  dry,  proofs  are  taken  to  determine  if  the  negative 
needs  any  further  treatment  in  the  way  of  strengthening,  re- 
ducing, or  local  touching  up  before  being  varnished. 

Intensification. — It  often  happens  that  the  negative  through 
over-exposure  or  under-development  lacks  sufficient  density  to 
give  good  prints.  In  such  cases  it  must  be  strengthened  or 
intensified.  This  is  done  by  causing  the  negative  to  take  a 
deposit  of  some  chemical  substance  in  order  to  produce  greater 
thickness  of  the  lines.  Intensifies  differ  according  to  the  na- 
ture of  the  sensitive  surface.  With  albumen  and  collodion  the 
most  common  intensifier  consists  of  a  mixture  of  gallic  and 
pyrogallic  acids  and  nitrate  of  silver  strongly  acidified  with 
acetic  acid.  For  gelatine  films  most  operators  employ  a  sat- 
urated solution  of  bichloride  of  mercury  ;  this  forms  the  chlo- 
ride of  silver  and  the  insoluble  proto-chloride  of  mercury 
which  is  deposited  on  the  film,  causing  it  to  assume  a  creamy 
tint,  which  is  changed  to  a  brown  or  black  by  subsequent 
treatment  with  a  solution  of  ammonia  or  sulphite  of  soda. 
Specific  instructions  for  the  use  of  these  and  other  intensifiers 
will  be  found  under  the  various  processes  described. 

Reduction. — Over-development  is  apt  to  produce  hard 
negatives  incapable  of  yielding  prints  full  of  soft  and  delicate 
gradations.  Such  negatives  may  often  be  made  fit  for  use 
by  reducing  the  excessive  thickness  of  the  deposit  of  metallic 
silver.  This  may  be  effected  by  treating  the  negative  with 
solutions  of  iodide,  cyanide,  or  the  perchlorides.  These  change 
the  deposit  on  the  film  into  the  iodide,  cyanide,  or  chloride  of 
silver,  which  are  then  dissolved  in  a  cyanide  or  hypo  bath. 

Success  in  this  treatment  is  by  no  means  certain,  owing  to 
the  impossibility  of  knowing  to  what  extent  the  metallic  silver 
has  been  converted  to  the  soluble  salt  until  the  negative  is 
taken  from  the  fixing-bath.  Keduction,  therefore,  is  to  be  re- 
sorted to  only  in  extreme  cases.  Other  methods  will  be  found 
in  Chapter  XI. 

Varnishing. — Collodion  negatives  must,  albumen  and  gela- 
tine negatives  should,  be  protected  from  chance  of  injury  by 
flowing  over  the  films  a  thin  coat  of  varnish.  If  the  negative 
does  not  require  touching  up,  any  good  negative  varnish  will 


PRELIMINARY    REMARKS    ON    EXPOSURE,    ETC.  31 

answer.  The  following  is  as  good  as  any  and  is  easily  made  : 
Dissolve  pure  yellow  lac  in  alcohol  in  the  proportions  of  150 
grains  of  lac  to  three  and  a  half  ounces  of  alcohol,  sp.  gr.  .83. 
Some  days  are  required  to  effect  solution,  during  which  the 
flask  is  occasionally  shaken.  The  varnish  is  then  well  filtered, 
and  is  applied  to  the  plate,  previously  slightly  warmed,  by 
pouring  it  upon  the  plate  held  in  a  horizontal  position.  When 
the  plate  is  well  covered  the  surplus  is  poured  off,  and  the 
varnish  dried  by  gentle  heat,  the  plate  being  rocked  to  pre- 
vent the  formation  of  ridges. 

A  good  retouching  varnish  is  made  as  follows : 

Sandarac .1  ounce 

Castor  oil 1  dram 

Alcohol 6  ounces 

The  sandarac  is  first  dissolved  in  the  alcohol,  after  which  the 
oil  is  added. 


CHAPTER  III. 

(JALOTVPE. 

THIS  is  the  name  which  Fox  Talbot  gave  to  the  process  by 
which  he  obtained  the  first  negatives  ever  made.  In  this 
process,  paper  of  a  fine  and  even  texture,  as  free  from  grain  as 
possible,  is  immersed  in  a  bath  containing  an  iodide,  and  when 
wanted  for  use  is  sensitized  on  a  bath  of  nitrate  of  silver,  and 
then  exposed. 

Plain  Saxe  or  Rives  paper  is  immersed  in  a  dilute  solution 
of  hydrochloric  acid,  the  acid  removed  by  thorough  washing, 
and  the  sheets  hung  up  to  dry.  As  soon  as  dry  they  are  ready 
to  be  treated  with  the  silver  iodide  bath,  made  as  follows : 

No.  1.  Silver  nitrate 46  grains 

Distilled  water 6  drams 

No.  2.  Potassium  iodide 46  grains 

Distilled  water 6  drams 

The  silver  iodide  is  formed  by  pouring  No.  2  into  No.  1,  with 
constant  stirring.  The  iodide  falls  to  the  bottom  of  the  beaker 
as  a  precipitate,  which  is  allowed  to  settle ;  the  water  is  then 
poured  off  as  closely  as  possible,  and  the  beaker  again  filled 
and  the  precipitate  well  stirred.  The  operation  is  repeated 
three  or  four  times  to  eliminate  the  bye-product,  potassium 
nitrate,  which  is  not  wanted. 

The  precipitate  is  then  dissolved  in  the  following  potassium 
iodide  solution : 

Potassium  iodide 462  grains 

Water 2J£  ounces 

This  is  poured  over  the  precipitate  and  well  stirred.  To 
insure  complete  solution,  crystals  of  the  potassium  salt  are 
added  with  constant  stirring  until  the  solution  turns  milky. 


CALOTYPE.  33 

The  solution  is  applied  to  the  paper  with  a  Buckle's  brush, 
made  by  inclosing  a  thin  tuft  of  cotton  in  the  loop  of  a  doubled 
string  passed  through  a  bore  of  a  piece  of  glass  tubing  six  or 
seven  inches  long.  The  loop  being  pulled  up  into  the  tube,  a 
brush  of  cotton  wool  is  formed. 

The  paper  is  cut  to  the  proper  size  and  pinned  to  a  flat 
board,  and  the  solution  is  brushed  over  its  surface,  brushing  up 
and  down  and  across,  to  secure  an  even  coating.  As  soon  as 
surface-dry  the  paper  is  immersed  in  a  dish  of  distilled  water, 
and  after  a  two-minutes  soaking  is  removed  to  a  second  dish, 
and  then  to*  a  third ;  care  must  be  taken  to  remove  all  air 
bells.  After  two  or  three  hours  soaking  the  potassium  iodide 
will  be  removed.  The  paper  is  then  hung  up  to  dry,  after 
which  it  may  be  preserved  in  any  convenient  way  for  future 
use,  but  as  it  is  somewhat  sensitive  to  light,  it  is  best  to  store  it 
in  a  dark,  dry  place. 

When  the  paper  is  wanted  for  use  it  is  sensitized  by  brush- 
ing over  it,  first  pinning  it  to  the  board  as  before,  a  mixture  of 
the  following  solutions : 

No.  1.  Silver  nitrate 77  grains 

Glacial  acetic  acid 2%  drams 

Water 14  drams 

No.  2.  Saturated  solution  of  gallic  acid  in  distilled  water 

To  every  dram  of  No.  1,  add  60  drams  of  distilled  water, 
then  1  dram  of  No.  2,  and  finally  30  drams  of  distilled  water. 
In  warm  weather  the  proportion  of  water  may  be  still  further 
increased  to  prevent  the  speedy  reduction  of  silver  nitrate, 
owing  to  the  presence  of  gallic  acid.  The  mixture  is  well 
stirred  and  applied  plentifully  to  the  surface  of  the  paper.  All 
excess  of  moisture  is  then  blotted  off  on  pure  filter  paper.  The 
paper  is  most  sensitive  while  moist,  but  it  will  give  images 
when  dry,  until  the  surface  of  the  paper  becomes  discolored 
owing  to  the  reduction  of  gallate  of  silver. 

For  exposure  the  paper  may  be  placed  between  two  pieces 
of  glass  and  inserted  in  the  holder,  or  if  preferred  it  may  be 
gummed  by  the  corners  to  a  glass  plate  or  piece  of  thick  paste- 
board. The  time  of  exposure  is  long,  varying  from  five  to 
twenty  minutes.  The  sensitiveness  may  be  increased  by 


34  THE    PHOTOGRAPHIC    NEGATIVE. 

increasing  the  proportions  of  the  silver  and  gallic  acid  in  the 
sensitizing  mixture,  but  the  keeping  qualities  of  the  prepared 
sheets  diminish  as  their  sensitiveness  increases.  It  has  been 
noticed  that  for  brilliantly  lighted  subjects  a  highly  sensitive 
condition  gives  the  best  results,  while  poorly  lighted  subjects 
require  a  paper  of  low  sensitiveness  to  avoid  fog. 

Development  is  effected  by  pinning  the  exposed  sheets  to  a 
board  and  applying  the  sensitizing  mixture  given  above  with 
the  brush.  As  soon  as  the  development  seems  to  flag,  the 
gallic  acid  solution  No  2  is  applied  sparingly  until  the  shadows 
begin  to  grow  dim. 

Under-exposed  pictures  require  more  of  No.  1.    If  the  iimge 
is  fairly  visible  before  development  the  paper  was  over  ex- 
posed ;  in  this  case  more  of  No.  2  should  be  added. 
~»      The  negative  is  fixed  in 

Sodium  hyposulphite 15  drams 

Water 35  ounces 

Fixing  is  complete  when  the  yellowness  of  the  iodide  is  no 
longer  visible  by  transmitted  light.  A  thorough  washing  for  three 
or  four  hours  in  many  changes  of  water  is  necessary  to  eliminate 
the  hypo.  When  dry  the  negative  can  be  printed  from  as  it  is, 
but  the  quality  of  the  prints  will  be  greatly  improved  by  waxing 
the  negative.  This  is  readily  done  by  heating  a  flat-iron  hot 
enough  to  melt  white  wax,  a  cake  of  which  substance  is 
applied  to  the  iron  as  it  passes  over  the  surface  of  the  paper. 
As  soon  as  the  negative  is  evenly  translucent,  a  sheet  of  blot- 
ting-paper is  laid  down  upon  it  and  the  iron  again  applied  to 
remove  all  superfluous  wax.  Care  must  be  taken  not  to  have 
the  iron  too  hot,  or  the  blotting-paper  will  absorb  too  much  of 
the  wax  and  cause  the  grain  of  the  paper  to  become  visible. 

The  above  is  a  description  of  the  method  by  which  Fox 
Talbot  obtained  his  first  negatives,  and  it  is  given  more  as  a 
matter  of  historical  interest  than  because  of  its  practical  value. 
The  great  disadvantage  of  this  and  other  like  methods  was  the 
rapid  deterioration  of  the  sensitized  sheets,  owing  to  the  com- 
bination of  the  silver  nitrate  with  the  vegetable  fibres  and  the 
sizing  of  the  papers,  and  also  to  the  formation  of  a  very  fugi- 
tive compound  of  iodo-nitrate  of  silver. 


CALOTYPE.  35 

Le  Gray,  in  his  once  famous  process,  by  waxing  the  paper 
before  sensitizing,  and  by  washing  away  all  excess  of  nitrate, 
greatly  increased  the  keeping  qualities  of  the  paper  but  dimin- 
ished its  sensitiveness,  and  M.  Pelegry,  a  French  amateur  who 
has  given  much  attention  to  the  process,  has  of  late  years  still 
further  increased  the  keeping  qualities  of  the  paper  and  has 
also  materially  decreased  the  time  of  exposure. 

LE  GRAY'S  PKOCESS. 

Waxing. — A  piece  of  thick  sheet-iron  is  placed  over  an  oil 
or  gas  stove  and  heated  up  to  the  melting  point  of  wax.  One 
or  two  sheets  of  blotting-paper  are  then  placed  on  the  iron,  and 
upon  these  a  sheet  of  the  paper  to  be  waxed.  This  is  evenly 
waxed  by  rubbing  it  with  a  piece  Qf  white  wax.  A  second 
sheet  is  laid  over  the  one  already  treated,  and  waxed  as  before. 
This  operation  is  continued  until  a  dozen  sheets  have  been  im- 
pregnated. The  sheets  are  then  separated  and  again  placed  on 
the  hot  iron  plate,  but  with  a  sheet  of  unwaxed  paper  between 
each  waxed  sheet.  The  pile  is  next  evenly  pressed  down  with 
a  pad  of  clean  blotting-paper,  being  frequently  turned  over. 
This  process  remelts  the  wax  and  impregnates  the  unwaxed 
sheets.  If  now,  on  separating  the  sheets,  any  of  them  show 
unwaxed  spots,  they  are  to  be  rewaxed  as  before,  one  at  a 
time. 

The  sheets  are  best  dried  by  placing  them,  separately  between 
blotting-papers,  or  two  unwaxed  sheets,  and  placing  them  on 
the  warm  iron  plate.  All  excess  of  wax  is  now  easily  removed 
by  using  the  pad  of  blotting  paper.  Excessive  heating  of  the 
plate  must  be  avoided  during  this  operation,  as  this  will  pro- 
duce a  grained  appearance  impossible  to  remove  by  rewaxing. 

The  iodide  lath.— 

Whey  (serum) 35  ounces 

Iodide  of  potassium 130  grains 

Bromide  of  potassium 30      " 

Milk  sugar  (crystals) 308      " 

NOTE. — The  whey  or  serum  is  produced  by  boiling  40  to  45 
ounces  of  milk.  As  soon  as  the  milk  boils  acetic  acid  is  added 
drop  by  drop  until  the  milk  is  coagulated.  The  liquid  is  then 


36  THE   PHOTOGRAPHIC    NEGATIVE. 

filtered  through  a  piece  of  linen  and  allowed  to  cool,  when  the 
white  of  an  egg,  beaten  to  a  froth,  is  added.  The  mixture  is 
again  boiled  to  coagulate  the  albumen,  which  clarifies  the 
serum.  The  liquid  is  ready  for  use  as  soon  as  filtered. 

As  this  bath  soon  ferments,  it  must  be  used  within  two  days 
of  its  preparation. 

The  bath  is  filtered  into  a  deep  porcelain  tray,  and  a  waxed 
sheet  is  first  floated  on  it,  avoiding  air  bubbles,  and  then  com- 
pletely immersed  in  it,  all  air  bells  being  removed  with  a  clean 
camel's  hair  brush  or  a  glass  triangle.  This  process  is  repeated 
until  a  sufficient  quantity  of  paper  has  been  immersed,  great 
care  being  taken  that  no  air  bells  are  allowed  to  form  between 
the  sheets.  After  soaking  for  two  hours  the  sheets  are  pinned 
up  by  one  corner  to  dry.  In  this  condition  they  will  keep  in- 
definitely. 

Sensitising. — The  sheets  are  immersed  one  after  the  other 
in  the  following  bath  : 

Distilled  water 3£  ounces 

Nitrate  of  silver 108    grains 

Glacial  acetic  acid ...  125  to  150    grains 

To  this  are  added  eight  to  ten  drops  of  the  iodide  solution 
given  above.  The  mixture  is  well  stirred  and  filtered  into  a 
porcelain  tray  used  only  for  this  purpose.  The  iodized  sheets 
are  to  be  immersed  in  this  bath  as  described  for  iodizing, 
avoiding  air  bells.  The  sheets  must  not  be  allowed  to  stick 
together,  and  each  one  is  turned  over  with  a  pair  of  bone  or 
glass  pincers  before  another  is  introduced. 

After  three  or  four  minutes  immersion  the  sheets  are  re- 
moved one  by  one  and  passed  successively  through  three  or 
four  baths  of  distilled  water.  They  are  then  placed  between 
sheets  of  strong,  pure  blotting-paper  and  all  excess  of  moisture 
removed,  after  which  they  are  dried  under  pressure  between 
fresh  blotters.  The  first  and  second  wash  waters  should  be 
renewed  for  every  three  or  four  sheets.  The  more  thorough 
the  washing  the  longer  the  sheets  will  keep,  but  the  less  their 
sensitiveness.  In  any  event  they  will  keep  only  two  or  three 
days. 


CALOTYPE.  37 

The  paper,  after  being:  iodized,  usually  loses  somewhat  of 
its  waxed  appearance,  which  can  be  restored  by  placing  the 
sheets  previous  to  sensitizing  between. blotters  and  smoothing 
with  a  warm  iron. 

Exposure. — The  prepared  sheets  are  made  ready  for  expos- 
ure as  in  Talbot's  process  and  the  exposure  varies  from  ten  to 
twenty  minutes,  according  to  circumstances. 

Development  and  Fixing. — These  operations  are  the  same 
as  in  Talbot's  method,  except  that  the  waxed  paper  is  im- 
mersed in  the  developer. 

Pelegry's  Process. — This  method  is  superior  to  the  forego- 
ing in  the  superior  keeping  qualities  which  it  confers  upon 
the  sensitized  sheets  and  in  its  greater  sensitiveness. 

Plain  Saxe  paper  is  immersed  for  a  few  moments  in  the 
iodide  bath  given  in  Le  Gray's  method,  and  hung  up  by  one 
corner  to  dry. 

When  wanted  for  use  the  dried  sheets  are  sensitized  by  a 
three  minutes  immersion  in  the  following  bath : 

Distilled  water 3^  ounces 

Nitrate  of  silver 154    grains 

Citric  acid 10    grains 

The  sheets  are  immersed  in  the  bath  as  in  Le  Gray's  pro- 
cess, but  no  more  than  five  sheets  must  be  sensitized  at  the 
same  time. 

After  remaining  in  the  bath  the  requisite  length  of  time, 
the  sheets  are  removed  one  by  one,  allowed  to  drain  slightly, 
and  placed  in  a  tray  containing  distilled  water.  Five  more 
sheets  are  then  sensitized  and  placed  with  the  others.  After 
a  short  soaking,  during  which  the  tray  is  rocked,  the  water  is 
poured  away,  and  a  fresh  supply  added.  The  tray  is  again 
rocked -for  a  few  moments  and  the  sheets  are  next  placed  in  a 
tray  containing  a  filtered  solution  of  chloride  of  sodium,  one 
to  one  hundred,  to  destroy  the  last  traces  of  nitrate  of  silver. 

After  a  short  sojourn  in  this  bath  they  are  well  washed  in 
several  changes  of  water,  and  finally  immersed  for  two  min- 
utes in  a  tannin  bath  made  as  follows : 

Two  hundred  and  thirty  grains  of  dextrine  are  macerated  in 
a  mortar  with  a  little  water ;  when  solution  is  complete  the 


38  THE    PHOTOGRAPHIC    NEGATIVE. 

bulk  is  made  up  to  twelve  ounces  of  water,  and  the  solution 
filtered.  To  this  is  added  a  filtered  solution  of  two  hundred 
and  thirty  grains  of  tannin  in  twelve  ounces  of  water,  and 
finally  forty-five  grains  of  gallic  acid  previously  dissolved  in 
four  drams  of  alcohol. 

After  treatment  with  this  preservative  the  paper  is  hung  up 
to  dry. 

Paper  prepared  as  above  and  preserved  in  a  dark  dry  place 
will  keep  good  from  three  to  six  months.  The  above  formulae 
will  prepare  18  by  22  sheets  of  paper. 

Exposure. — Well-lighted  landscapes  require  from  five  to 
six  minutes  exposure.  Sombre  views  will  require  at  least 
thirty  minutes  for  full  exposure. 

Development. — The  development  should,  if  possible,  be  ef- 
fected within  a  few  hours  of  exposure,  but  in  case  of  necessity 
it  may  be  deferred  for  some  days. 

The  developer  is  thus  compounded  : 

Water 3i  drams 

Pyrogallic  acid 15    grains 

Citric  acid 15    grains 

The  sheet  to  be  developed  is  first  moistened  in  a  tray  con- 
taining pure  water  and  then  immersed  in  the  pyro  solution,  in 
which  it  is  turned  several  times  to  insure  equalization  of  the 
developer.  The  negative  is  then  removed  from  the  developer 
to  which  a  dram  or  two  of  a  three  to  one  hundred  solution  of 
nitrate  of  silver  is  added :  the  tray  is  rocked  to  insure  an  equal 
mixture,  and  the  negative  is  again  placed  in  the  solution. 
The  image  soon  appears  and  development  is  arrested  as  soon 
as  the  details  are  well  out  and  the  density  seems  sufficient,  the 
tray  being  well  rocked.  The  negative  is  then  washed  in  two 
changes  of  water  and  fixed  in  a  one  to  six  hyposulphite  of 
soda  solution,  in  which  it  is  allowed  to  remain  from  thirty  to- 
forty  minutes.  It  is  then  well  washed  and  dried  between 
blotting-papers.  As  soon  as  dry  it  is  ready  for  oiling,  which 
may  be  done  as  best  suits  the  operator's  taste  and  convenience,, 
either  with  castor  oil,  translucine,  vaseline,  or  wax. 


OHAPTEK  IV. 

SESSITIVE  SURFACES  ON  GLASS.    PREPARATION  OP  THE  GLASS. 

THE  glass  plates  should  be  selected  with  great  care.  They 
should  be  flat,  and  free  from  scratches  and  bubbles.  For  small 
sizes  ordinary  glass  of  good  manufacture  will  answer,  but  for 
large  pictures  and  process  work,  plate,  or  patent-plate,  should 
be  used.  The  rough  edges  should  be  smoothed  down  with  a 
flat  file,  and  the  glasses  should  never  be  packed  with  pieces  of 
printed  paper  between  them,  since  printer's  ink  is  apt  to  leave 
greasy  spots  on  the  plates,  which  must  be  perfectly  clean 
before  they  are  coated  with  the  collodion  or  emulsion.  New 
plates  should  be  soaked  for  some  hours  in  a  solution  of 
carbonate  of  soda,  and  then  well  washed  and  soaked  for  some 
time  in  a  solution  of  equal  parts  of  nitric  acid  and  water.  They 
are  then  well  washed  and  dried,  if  not  to  be  albumenized. 
Old  collodion  plates  should  be  immersed  over  night  in  the  fol- 
lowing solution  : 

Sulphuric  acid 1  ounce 

Bichromate  of  potash 1  ounce 

Water 16  ounces 

and  then  washed. 

This  solution  quickly  destroys  organic  substances,  but  it  must 
be  renewed  as  soon  as  crystals  are  formed. 

In  all  cases  it  is  well  to  drain  the  plates  on  blotting  paper, 
and  to  rub  them  dry  with  a  piece  of  canton-flannel,  which  is 
used  for  no  other  purpose. 

The  Final  Cleaning  of  the  Glasses  for  the  Albumen  and 
Collodion  Processes. — After  the  preliminary  treatment  with 
acid  or  bichromate  of  potash  the  dried  plates  are  breathed  on 
and  rubbed  with  a  clean  towel  kept  for  this  purpose  exclu- 
sively. It  is  important  that  the  fingers  do  not  touch  the  plate. 


40  THE    PHOTOGRAPHIC    NEGATIVE. 

The  towel  is  spread  out  on  a  clean  table,  the  plate  is  laid  upon 
it,  and  one  end  of  the  towel  is  folded  over  one  edge  of  the 
plate,  which  is  then  rubbed  with  the  other  end  of  the  towel. 

After  both  sides  and  the  edges  of  the  plates  have  been 
thoroughly  rubbed,  it  is  tested  by  breathing  upon  it  and  ex- 
amining it  by  reflected  light.  If  it  is  perfectly  clean  the 
moisture  of  the  breath  will  evaporate  evenly.  If,  however,  it 
shows  spots  it  must  be  again  breathed  on  and  rubbed.  If  this 
fails  to  remove  the  spots,  the  plate  must  be  returned  to  the 
acid  bath.  "When  the  plate  appears  perfectly  clean  after  this 
treatment,  it  is  ready  for  the  final  polishing,  which  is  done 
with  chamois  leather  pads.  The  plate  may  be  held  in  a  clean- 
ing vice  or  laid  on  a  clean  towel.  A  small  quantity  of  alcohol 
is  then  poured  on  the  plate  and  rubbed  over  it  with  one 
of  the  pads ;  the  plate  is  next  polished  with  another  pad,  and 
may  be  considered  finished  when  it  takes  the  breath  evenly. 

Instead  of  alcohol,  old  and  worthless  collodion  is  often  used. 
Varnished  plates  must  be  soaked  for  some  hours  in  a  solution 
of  soda ;  they  are  then  washed  with  water,  soaked  in  the  acid 
bath,  washed,  and  polished  as  above. 

The  towels  and  chamois  skins  used  for  cleaning  and  polish- 
ing must  be  washed  in  soda,  never  with  soap. 

Albumenizing  the  Glasses. — In  order  to  avoid  the  tedious 
operation  of  polishing,  many  operators  prefer  to  flow  an  albu- 
men solution  over  the  plate  after  it  has  been  treated  with  the 
acid  bath  given  above.  The  following  solution  is  poured  over 
the  plate  while  still  wet : 

Whites  of  2  eggs 

Water 64  ounces 

Ammonia 1  dram 

Iodide  of  potassium %  dram 

This  is  placed  in  a  bottle  containing  glass  broken  up  into 
small  pieces  and  well  shaken  for  fifteen  minutes ;  it  is  then 
filtered  and  flowed  over  the  glasses,  the  surplus  being  drained 
away  to  waste.  The  plates  are  racked  away  to  dry  in  a  room 
free  from  dust.  They  will  keep  for  a  month,  and  give  as  good 
results  as  those  which  have  been  polished. 


SENSITIVE  SUKFACES  ON  GLASS.  41 

TREATMENT   OF  THE   GLASSES   FOR  THE   GELATINE   EMULSION 
PEOCESS. 

The  glass  of  old  negatives  which,  for  any  cause,  have  become 
useless  for  printing,  may  be  again  coated  after  the  films  have 
been  removed.  The  simplest  method  of  removing  old  films  is 
to  soak  the  plates  in  a  moderately  strong  solution  of  hydro- 
chloric acid  until  the  films  are  easily  detached  from  the  glasses, 
which  after  being  well  washed  in  clean  warm  water  and  rubbed 
with  a  coarse  cloth  to  remove  all  adhering  pieces  of  film,  are 
ready  for  further  treatment. 

Cleaning  the  Glass. — Both  old  and  new  glass  should  be 
soaked  in  a  ten  per  cent,  solution  of  nitric  acid,  then  well 
washed,  and  immersed  in  a  solution  of  carbonate  of  soda  con- 
taining a  little  alcohol.  The  plates  while  in  this  solution  are 
well  rubbed  with  a  clean  cloth,  then  washed  in  clean  cold  water 
until  it  flows  evenly  over  them,  rinsed  in  distilled  water,  and 
stood  up  to  dry  on  blotting-paper.  When  dry  they  should 
be  well  wrapped  up  to  prevent  dust  from  settling  on  them. 

Polishing  with  Talc. — When  the  films  are  to  be  stripped  from 
the  glass  after  fixing,  the  plates  must  be  polished  with  French 
chalk.  This  is  done  by  dusting  a  little  of  the  chalk  over  them 
and  polishing  with  a  clean  piece  of  linen,  using  a  circular 
motion.  All  excess  of  chalk  is  dusted  off  with  a  camel's-hair 
brush.  The  plates  are  then  flowed  with  plain  collodion,  and 
•coated  with  the  emulsion  when  the  collodion  is  dry. 

Substrata. — It  is  the  practice  of  many  coaters  to  give  the 
plates  a  substratum  of  some  kind  to  prevent  blisters,  or  to  as- 
sist the  flowing  of  the  emulsion.  A  few  of  the  best  of  these 
substrata  are  here  given. 

1. — White  of  egg-. 1  ounce 

Water 20  ounces 

Alcohol 1  ounce 

Carbolic  acid 20  drops 

Add  the  carbolic  acid  to  the  alcohol,  and  stir  well ;  then  pour 
the  mixture  into  the  albumen  and  water  which  have  been  pre- 
viously mixed,  then  filter. 


42  THE    PHOTOGRAPHIC    NEGATIVE. 

DR.  VOGELS. 

2.— a.— Gelatine 150  grains 

Acetic  acid %  ounce 

Dissolve  by  heat. 

b.— Chrome  alum 10  grains 

Water K  ounce 

For  use  take  of  a,  2^  parts  ;  Z>,  1  part ;  alcohol,  70  parts,  and 
filter.  Coat  the  plates  as  with  collodion. 

3. — Soluble  water  glass 1  ounce 

Albumen .   8  ounces 

Water Bounces 

The  wet  plates  are  coated  with  this  solution,  drained, 
dried,  and  washed. 

4.— Gelatine 75  grains 

Distilled  water 60  ounces 

Ammonia 2  drams 

Alcohol 1  ounce 

Soak  the  gelatine  in  half  the  given  quantity  of  water,  then 
add  the  remaining  half  at  the  boiling  point ;  when  cool  add  the 
ammonia  and  alcohol,  and  filter. 

5. — White  of  egg 1  ounce 

Water 100  ounces 

Ammonia 5  drops 

Shake  well  for  five  minutes,  and  then  filter. 

6. — India  rubber 10  grains 

Water 1  ounce 

Filter  and  flow  over  the  plates  like  collodion. 

More  care  must  be  taken  in  cleaning  the  plates  when  a  sub- 
stratum is  to  be  used,  the  difficulty  being  to  secure  an  even 
coating. 

Instead  of  flowing  the  above  solutions  over  the  plates,  they 
may  be  applied  with  a  Blanchard  brush,  which  is  made  by  tie- 
ing  a  double  thickness  of  fine  canton-flannel,  ribbed  side  out, 
over  one  end  of  a  strip  of  glass  about  six  inches  long  and  two 


SENSITIVE    SURFACES   ON    GLASS. 


inches  wide.  The  brush  is  dipped  in  the  solution  and  the  ex- 
cess squeezed  out  against  the  side  of  the  beaker.  The  plate  is 
then  brushed  smoothly  down  the  surface  in  parallel  lines.  In 
this  way  a  thin  and  even  coating  is  applied. 


CHAPTEK  Y. 

THE    ALBUMEN    PROCESS. 

.  THE  second  step  in  the  development  of  the  negative  process 
was  the  employment  of  albumen  as  a  vehicle  for  the  suspen- 
sion of  the  finely-divided  sensitive  salts,  and,  in  consequence, 
the  use  of  glass  as  the  means  of  support.  Niepce  de  Saint 
Yictor  seems  to  have  been  the  first  to  work  out  a  practical 
method  for  the  use  of  albumen,  and  the  process  was  greatly 
improved  by  later  experimenters. 

Although  rarely  used  to-day,  the  process  is  a  valuable  one 
for  delicate  work,  where  the  utmost  possible  fineness  of  grain 
is  desired. 

The  drawbacks  to  the  more  general  adoption  of  a  process 
which  undoubtedly  yields  the  very  finest  photographic  results, 
are,  the  long  exposure  necessary,  the  difficulty  of  securing  an 
even  coating  of  the  extreme  tenuity  required  to  prevent  the 
film  from  leaving  the  glass,  and  the  extreme  care  demanded 
to  prevent  dust  from  settling  on  the  films  while  drying. 
Methods  of  overcoming  these  difficulties  will  be  given  under 
the  practical  manipulations  soon  to  be  described. 

The  general  outline  of  the  process  is  as  follows :  The  whites 
of  several  eggs  are  carefully  separated  from  the  yolks  and 
germs,  and  beaten  to  a  froth  with  a  bundle  of  quill  pens  or  a 
wooden  fork.  After  standing  for  some  hours,  the  deposit  of 
albumen  is  decanted  and  filtered  by  upward  filtration,  as  de- 
scribed on  page  19. 

An  addition  of  an  aqueous  solution  of  iodide  and  bromide 
of  potassium  or  ammonium  is  then  made,  and  the  mixture  is 
well  stirred  and  filtered  as  before.  From  this  point  on,  the 
greatest  precautions  must  be  taken  to  prevent  particles  of  dust 
from  settling  in  the  mixture. 


THE   ALBUMEN   PKOCESS.  45 

The  plates,  which  must  be  plate  or  patent  plate,  are  next 
coated  and  dried  in  a  perfectly  horizontal  position.  In  this 
condition,  the  plates  are  insensitive,  and  will  keep  for  an 
indefinite  period.  They  should  be  stored  in  a  dust-proof  box. 
When  wanted  for  use,  they  are  sensitized  by  an  immersion  in 
a  nitrate  of  silver  bath  acidified  with  glacial  acetic  acid.  The 
effect  of  this  bath  is  to  coagulate  the  albumen,  to  form  the 
albuminate  of  silver,  and  to  transform  the  soluble,  insensitive 
iodide  and  bromide  into  the  insoluble  and  sensitive  iodide  and 
bromide  of  silver.  Therefore,  the  operation  of  sensitizing 
must  be  performed  in  yellow  light. 

After  being  sensitized,  the  plates  are  washed  in  many 
changes  of  pure  filtered  water,  to  remove  all  traces  of  nitrate 
of  silver;  they  are  then  dried  by  heat  and  are  ready  to  be 


GOBERT'S  ALBUMEN  METHOD. 

Formulae. 
No.  1.— THE  ALBUMEN  MIXTURE. 

Albumen  from  fresh  eggs   26  drams 

Iodide  of  ammonium 15  grains 

Bromide  of  potassium 4  grains 

Iodine  in  pellets 4  grains 

First  dissolve  the  salts  in  two  ounces  of  water  and  then  dis- 
solve the  iodine.  Then  add  the  solution  to  the  albumen,  beat 
to  a  froth,  and,  after  standing  for  some"  hours,  decant  the  albu- 
men and  filter  twice,  as  described  above. 

No.  2.— THE  SENSITIZING  BATH. 

Distilled  water 4  ounces 

Nitrate  of  silver 155  grains 

Glacial  acetic  acid 2%  drams 

MANIPULATIONS. 

Cleaning  the  Glass. — Pour  a  few  drops  of  hydrochloric  acid 
on  the  surface  of  the  glass  plate,  previously  freed  from  all  im- 
purity by  soaking  first  in  a  solution  of  caustic  potash,  then  in 
dilute  nitric  acid,  and  well  washed  under  the  tap.  Then  polish 


46  THE   PHOTOGRAPHIC   NEGATIVE. 

with  a  dabber  of  cotton  dipped  in  the  following  iodine  solu- 
tion : 

Iodine 4  grains 

Alcohol 4  ounces 

This  is  well  rubbed  in,  and  the  plate  dried  with  a  piece  of 
fine  linen. 

Coating. — A  sufficient  quantity  of  solution  No.  1  is  poured 
over  the  plate,  which  is  held  in  the  left  hand  by  means  of  a 
pneumatic  holder  having  a  vertical  handle  provided  with  a 
small  brass  hook  at  the  end.  The  albumen  should  be  poured 
in  a  pool  on  the  right-hand  upper  corner  of  the  plate.  When 
the  surface  of  the  plate  is  completely  covered,  to  effect  which 
some  coaxing  with  a  glass  rod  may  be  necessary,  the  excess  is 
drained  off  in  a  reserve  flask  for  filtration. 

A  pipette  will  be  found  very  convenient  for  getting  the 
albumen  on  the  plate  free  from  bubbles. 

After  draining  as  closely  as  possible,  the  plate  is  rocked 
gently  to  equalize  the  film.  If  any  specks  of  dust  or  air  bells 
are  noticed,  they  must  be  removed  with  the  point  of  a  clean 
piece  of  paper,  or  with  the  pipette. 

Notwithstanding  the  close  draining,  the  film  is  still  too 
thick  ;  it  must  be  made  thinner,  and  at  the  same  time  equal- 
ized. This  is  done  by  suspending  it,  film  down,  by  catching 
the  hook  in  the  handle  in  the  loop  of  a  doubled  string  hanging 
from  the  ceiling  of  the  room.  A  slow  rotary  movement  is 
then  given  to  the  plate.  -  The  centrifugal  force  thus  generated 
throws  off  all  excess  of  albumen,  and  equalizes  the  film  except 
along  the  edges,  where  ridges  are  formed  which  are  dried  with 
blotting-paper  when  the  plate  is  removed  from  the  string. 

In  order  to  avoid  spots  of  albumen  on  the  floor  and  walls,  it 
is  best  to  suspend  the  plate  in  a  large  round  metallic  tray. 

Drying  the  Plate. — The  plate  must  be  dried  rapidly,  and  in 
a  perfectly  horizontal  position.  Perhaps  the  best  method  of 
combining  these  requisites,  while  at  the  same  time  reducing  to  a 
minimum  the  danger  of  dust  falling  on  the  film,  is  to  place 
the  plate  film  downwards  on  three  levelling  screws  provided 
with  needle  points  ;  these  screws  stand  on  an  iron  plate  placed 
over  an  oil  or  gas  stove. 


THE    ALBUMEN    PROCESS.  47 

The  old  daguerreotype  gilding  stand  will  be  found  a  very 
convenient  drying  apparatus.  If  neither  of  these  means  are  at 
hand,  the  plate  may  be  dried  by  placing  it  on  a  warm  iron 
plate  film  up,  first  putting  two  or  three  sheets  of  blotting- 
paper  on  the  iron  to  equalize  the  heat. 

Fuming  with  Vapors  of  Iodine. — The  action  of  the  sensit- 
izing bath  is  greatly  assisted  by  fuming  the  dried  film  with  the 
vapors  of  iodine.  The  simplest  way  of  doing  this  is  to  cut  a 
rectangular  opening,  somewhat  smaller  than  the  plate,  in  the 
cover  of  a  wooden  box  four  or  five  inches  in  depth.  Some 
pellets  of  iodine  are  placed  in  the  bottom  of  the  box,  and  the 
plate  is  laid  over  the  opening  in  the  cover  film  down,  and 
fumed  until  it  assumes  a  rich  golden  hue.  It  is  then  taken 
from  the  box,  and  after  a  short  exposure  to  the  atmosphere  to 
allow  the  excess  of  iodine  to  volatilize,  it  is  ready  to  be  sen- 
sitized. 

Sensitizing. — The  plate  is  sensitized  in  yellow  light  by  a 
three  minute  immersion  in  solution  No.  2,  above.  It  is  then 
well  washed  in  several  changes  of  water,  allowed  to  drain,  and 
the  preservative,  a  saturated  solution  of  gallic  acid,  is  flowed 
over  it.  It  is  then  dried  by  gentle  heat.  The  dried  plates 
will  retain  their  good  qualities  for  some  weeks.  The  films 
should  have  a  decided  opalescent  appearance.  If  this  is  want- 
ing, the  film  is  too  thin,  owing  to  a  too  rapid  rotation  on  the 
pneumatic  holder.  The  remedy  is  obvious.  The  time  of  ex- 
posure varies  from  10  to  30  minutes,  according  to  circumstances. 

Development. — The  exposed  plates  are  developed  in  a  bath 
containing  a  saturated  solution  of  gallic  acid,  to  which  has  been 
added  a  few  drops  of  a  1  to  30  solution  of  nitrate  of  silver. 

The  process  should  not  be  unduly  hastened  ;  the  best  results 
are  gained  by  slow  development.  The  developer  must  be 
thrown  away  when  it  becomes  cloudy. 

The  developer  thus  compounded  will  bring  out  all  the  details 
and  give  good  printing  density  on  properly  exposed  plates.  If, 
however,  the  image  shows  a  lack  of  detail  and  density  after 
prolonged  development,  a  fresh  developer,  containing  gallic 
acid  and  silver,  must  be  compounded. 

Fixing. — After  development  the  plate  is  rinsed  in  clean 


48  TllE    PHOTOGRAPHIC    NEGATIVE. 

water  and  immersed  in  a  ten  per  cent,  solution  of  hyposulphite 
of  soda  until  the  opalescent  appearance  has  disappeared.  It  is 
then  well  washed  in  running  water,  to  eliminate  the  hypo,  and 
when  dry  it  is  ready  to  be  printed  from. 

VARIOUS  MODIFICATIONS  OF  THE  ALBUMEN  PROCESS. 

Numerous  experiments  have  been  made  by  different  investi- 
gators to  shorten  the  time  of  exposure  by  introducing  various 
modifications,  consisting  chiefly  in  the  use  of  a  larger  propor- 
tion of  iodide  and  the  addition  of  certain  substances  to  produce 
a  more  porous,  and,  therefore,  more  sensitive  film.  A  few  of 
the  best  of  these  are  here  given. 

Sellers  Modification. — 

Water 5  drams 

White  sugar 120  grains 

Iodide  of  potassium 61  grains 

Iodine  in  pellets 12  grains 

Bromide  of  potassium. 12  grains 

Pour  the  solution  into  14  ounces  of  albumen,  beat  to  a  froth, 
and,  after  standing  for  twenty-four  hours,  decant  three-fourths 
of  the  liquid  for  use.  The  remaining  manipulations  are  the 
same  as  described  above. 

tiagofs  Modification. — 

Dextrine 140  grains 

Iodide  of  potassium 46  grains 

Bromide  of  potassium 8  grains 

Distilled  water 11  drams 

Dissolve  by  heat,  filter  and  add  the  whites  of  six  eggs.  All 
the  other  operations  are  as  described  above,  with  the  following 
exceptions  :  Sensitize  on  a  ten  per  cent,  solution  of  nitrate  of 
silver,  containing  twenty -five  per  cent,  of  glacial  acetic  acid, 
and  develop  in  the  following  bath  : 

Distilled  water •. 12)^  ounces 

Gallic  acid 108  grains 

Acetate  of  lime  46  grains 

at  a  temperature  varying  from  120  to  140  deg. 


THE    ALBUMEN    PROCESS.  49 

Couppier's   Modification. — 

Albumen 25  drams 

Distilled  water 6)^  drams 

Iodide  of  potassium 15  grains 

The  manipulations  are  the  same  as  in  Gobert's  method. 

The  Albumen  Honey  Process. — The  following  description 
of  this  process,  as  formerly  worked  by  Whipple  and  Black,  is 
taken  from  the  Photographic  Times.  The  plates  are  given  a 
thin,  even  coating  of  the  following  solution  : 

Albumen 8  ounces 

Honey 7  ounces 

To  which  has  been  added 

Iodide  of  potassium .v 3  grains 

Bromide  of  potassium 20  grains 

Chloride  of  sodium 10  grains 

Water 2  ounces 

The  mixture  is  beaten  to  a  stiff  froth,  allowed  to  settle,  and 
then  filtered. 

The  dried  plates  are  sensitized,  while  still  warm,  in  the  fol- 
lowing bath : 

Nitrate  of  silver 1  ounce 

Acetic  acid,  No.  8 8  to  10  drams 

Water 10  ounces 

The  plate  is  kept  in  constant  motion  while  in  the  bath. 
After  sensitizing,  the  plates  are  washed  slightly,  if  to  be  used 
immediately.  If,  however,  they  are  to  be  kept  for  any  length 
of  time,  they  must  be  washed  until  all  the  silver  is  washed 
away.  Development  is  effected  in  a  saturated  solution  of 
gallic  acid,  to  which  a  few  drops  of  a  nitrate  of  silver  solution 
have  been  added. 


CHAPTER  VI. 

THE    COLLODION    PROCESS,    WET-PLATES. 

LB  GKAY  was  the  first  to  suggest  collodion  as  a  vehicle  for 
the  suspension  of  the  salts  of  silver  in  place  of  the  albumen 
method  of  St.  Victor.  To  Scott  Archer  and  Dr.  Diamond, 
however,  belong  the  credit  of  having  been  the  first  to  intro- 
duce the  collodion  process  in  the  practical  form  in  which  it  is 
still  used. 

This  was  in  1851,  and  the  publication  of  their  process  revo- 
lutionised photographic  methods,  and  incited  many  experi- 
menters to  investigate  the  new  process. 

It  would  be  impracticable  to  enter  into  a  detailed  discussion 
of  the  improvements  discovered  by  such  patient  investigators 
as  Martin,  Gaudin,  Spiller,  Sutton,  Schnauss,  Carey  Lea, 
Sdronheim,  Roettcher,  Bellitzky,  Vogel,  Eder,  Duchochois, 
and  others,  to  all  of  whom  photography  is  deeply  indebted. 
The  history  of  photography  has  been  ably  treated  in  another 
volume  of  this  series,  and  need  not  be  repeated  here. 

The  advent  of  gelatine  plates  by  no  means  sounded  the 
death  knell  of  collodion.  It  is  still  in  common  use  by  not  a 
few  of  our  best  practitioners  in  all  cases  where  the  extreme  of 
rapidity  is  not  called  for,  and  in  the  opinion  of  many  good 
judges  collodion  negatives  possess  qualities  which  are  only 
with  extreme  difficulty  conferred  upon  gelatine  plates. 

For  these  reasons,  the  process  is  fully  described  in  all  its 
details,  as  practised  by  the  best  operators. 

The  base  of  collodion  is  the  substance  known  as  pyroxyline, 
or  soluble  gun-cotton,  which  is  prepared  by  submitting  cotton, 
paper,  or  other  like  substances,  to  the  action  of  a  mixture  of 
sulphuric  and  nitric  acids.  The  resulting  substance,  when  dis- 
solved in  a  mixture  of  ether  and  alcohol,  forms  the  volatile, 
viscous  compound  known  as  collodion. 


THE    COLLODION   PROCESS,    WET-PLATES.  51 

The  preparation  of  pyroxyline  suitable  for  photographic 
work  is  a  somewhat  delicate  operation,  and,  as  a  rule,  it  is  wise 
to  purchase  it  ready-made  of  the  dealer.  The  two  formulae 
for  its  manufacture  which  are  given  below,  are  recommended 
by  Hardwich,  who  at  one  time  made  many  experiments  in  this 

direction. 

No.  1. 

Sulphuric  acid,  sp.  gr.  1.842  at  59  deg.  F 18      ounces 

Nitric  acid,  sp.  gr.  1.456 6      ounces 

Water   — 4%  ounces 

Cottonwool  360      grains 

No.  2. 

Sulphuric  acid,  1.842 6      o.unces 

Nitrate  of  potassium 3^  ounces 

Cotton  wool 62      ounces 

Water 1      ounce 

Mr.  Abney  says  the  cotton  must  be  first  well  steeped  in  an 
aqueous  solution  of  carbonate  of  soda,  and 'then  be  well  washed 
and  perfectly  dried.  It  should  then  be  made  up  into  ten  or 
twelve  balls. 

The  nitrate  of  potassium  should  be  as  free  from  chloride  of 
potassium  as  possible,  and  dried  in  an  air  bath  at  a  temperature 
of  about  120  deg. 

The  water  and  nitric  acid  are  poured  into  a  porcelain  dish 
and  well  mixed,  then  the  sulphuric  acid  is  added  with  constant 
stirring.  The  temperature  will  rise  to  about  170  deg.,  and 
the  liquid  must  be  allowed  to  cool  down  to  about  150  deg. 
The  balls  of  cotton  are  then  immersed  separately  in  the  liquid, 
as  rapidly  as  possible,  to  prevent  decomposition.  After  receiv- 
ing a  thorough  soaking,  using  a  glass  or  porcelain  spatula  to 
keep  the  balls  submerged,  they  are  allowed  to  remain  ten  or 
fifteen  minutes  in  the  solution.  They  are  then  raised  by  the 
spatula,  as  much  of  the  liquid  as  possible  being  extracted  by 
pressing  them  against  the  side  of  the  dish,  and  then  they  are 
placed  in  a  large  vessel  full  of  clean  water.  The  washing 
must  be  continued  until  a  piece  of  blue  litmus  paper  retains 
its  color  after  two  or  three  minutes'  contact  with  the  cotton, 
which,  when  dried,  should  weigh  about  25  per  cent,  more  than 
the  original  cotton. 


52  THE   PHOTOGRAPHIC   NEGATIVE. 

It  is  important  that  the  acids  be  of  the  specific  gravity  indi- 
cated in  the  formulae,  as  any  deviation  will  materially  change 
the  character  of  the  pyroxyline.  The  second  formula  is  usu- 
ally to  be  preferred. 

The  Solvents. — Alcohol  and  ether  in  varying  proportions 
are  the  solvents  of  pyroxyline  employed  in  the  manufacture 
of  collodion.  Many  modifications  may  be  made  in  the  film  by 
altering  the  proportions  of  the  solvents.  Up  to  a  certain 
point  an  increase  in  the  quantity  of  alcohol  confers  greater 
sensitiveness  and  density.  It  must  not  be  too  largely  in  ex- 
cess, however,  or  tender,  porous  films  will  result. 

An  excess  of  ether  gives  strong,  contractile  films,  which  are 
easily  stripped  from  the  glass.  The  specific  gravity  of  the 
alcohol  must  be  varied  to  suit  the  sample  of  pyroxyline  used 
in  making  up  the  collodion. 

For  pyroxyline  prepared  at  a  high  temperature  the  alcohol 
should  have  a  spec-iric  gravity  of  .812.  For  the  tougher 
variety  of  pyroxyline  a  specific  gravity  of  .820  is  about  right. 

The  ether  should  be  as  pure  as  possible. 

The  normal  proportion  of  the  solvents  is  equal  volumes  of 
each,  but  this  may  be  modified  as  required. 

The  lodizers. — These  are  the  various  metallic  iodides  and 
bromides  which  are  added  to  the  collodion  to  produce,  when 
the  plate  is  immersed  in  the  silver  bath,  the  sensitive  iodide  and 
bromide  of  silver.  Obviously  only  those  iodides  and  bromides 
can  be  used,  which  are  soluble  in  alcohol  and  ether.  Those 
most  commonly  employed  are  the  iodides  and  bromides  of 
potassium,  ammonium,  calcium,  cadmium,  sodium,  and,  more 
rarely,  lithium. 

These  are  not  all  of  equal  value  for  the  preparation  of  the 
salted  collodion.  Three  factors  determine  the  choice  of  the 
Boluble  salt,  viz.,  the  physical  action  of  the  salts ;  the  perman- 
ency of  the  resulting  collodion,  and  the  solubility  of  the  salt. 

Cadmium,  although  very  soluble  and  giving  a  collodion  of 
good  keeping  qualities,  has  a  tendency  to  thicken  the  film, 
and  must,  therefore,  be  used  with  caution  and  only  in  connec- 
tion with  other  salts. 

The  iodides  of  potassium  and  ammonium  give  more  intense 


THE   COLLODION    PROCESS,    WET-PLATES.  53 

images  than  the  iodide  of  cadmium,  but  they  are  not  so  solu- 
ble and  the  resulting  collodion  does  not  keep  so  well. 

The  salts  of  sodium  and  lithium  are  but  rarely  used  on  ac- 
count of  their  decomposing  action. 

A  collodion  containing  iodide  alone  gives  great  density  with 
little  detail  in  the  shadows,  one  containing  bromide  only  gives 
less  density  but  more  detail  in  the  shadows. 

For  this  reason  the  common  practice  is  to  use  mixed  collo- 
dion for  general  work  to  secure  both  density  and  detail. 

Plain  Collodion. — It  is  customary  to  make  up  a  stock  of 
plain  collodion  to  be  iodized  in  sufficient  quantity  for  the 
work  in  hand.  This  plain  collodion  can  be  kept  indefinitely 
in  well-stoppered  bottles.  The  following  formulae  are  given 
for  its  preparation : 

FOR  COLD  WEATHER. 

Pyroxyline 185  to  215  grains 

Alcohol 16  ounces 

Ether 19  ounces 

FOR  WARM  WEATHER. 

Pyroxyl  ine 185  to  215    grains 

Alcohol   17J  ounces 

Ether 17£  ounces 

The  quantity  of  pyroxyline  may  be  increased  if  desired, 
but  it  should  not  exceed  two  per  cent.  An  increase  in  pyroxy- 
line increases  the  sensitiveness  but  diminishes  the  flowing 
quality  of  the  collodion. 

The  usual  method  of  making  up  the  plain  collodion  is  to 
add  the  pyroxyline  to  the  alcohol  and  then  to  add  the  ether  in 
small  quantities,  shaking  well  after  each  addition. 

Some  operators,  however,  prefer  to  add  the  pyroxyline  to 
the  ether,  shaking  it  up  well  until  the  fibres  are  well  dis- 
tended, and  then  to  add  the  alcohol  in  small  quantities  with 
constant  shaking. 

In  either  case  the  solution  is  allowed  to  stand  for  twenty- 
four  hours  before  being  used.  Sufficient  of  the  clear  liquid 
for  the  work  to  be  done  is  then  decanted  off. 

Salted  Collodion. — Plain  collodion  is  iodized  or  salted  by 
the  addition  of  soluble  iodides  or  bromides,  or  both. 


54:  THE    PHOTOGRAPHIC   NEGATIVE. 

The  following  formulae  will  be  found  suitable  for  general 
landscapes,  and  portrait  work : 

BROMIZED  COLLODION. 

Bromide  of  zinc 247  grains 

Plain  collodion   35  ounces 

IODIZED  COLLODION. 

a.  Iodide  of  ammonium 123  grains 

Plain  collodion 35  ounces 

b.  Iodide  of  cadmium 154  grains 

Plain  collodion 35  ounces 

a  must  be  used  at  once  ;  5  will  keep  indefinitely. 
BROMO-IODIZED  COLLODION. 

a.  Iodide  of  ammonium 108  grains 

Bromide  of  cadmium 62  grains 

Plain  collodion 35  ounces 

b.  Iodide  of  cadmium 139  grains 

Bromide  of  cadmium 62  grains 

Plain  collodion 35  ounces 

a  can  be  used  soon  after  making ;  b  must  be  allowed  to 
ripen  for  some  time  before  it  will  flow  well. 

Another  method  of  salting  the  collodion  is  to  add  to  ninety 
parts  of  plain  collodion,  ten  parts  of  the  following  bromo- 
iodide  solution  : 

Absolute  alcohol 7f  ounces 

Iodide  of  cadmium 154    grains 

Bromide  of  cadmium 154    grains 

Iodide  of  ammonium 154    grains 

Mr.  John  CarbutCs  Methods. — Mr.  Carbutt  first  prepares 
the  double  salts  of  potassio-cadmium  iodide  and  ammonio- 
cadmium  bromide  with  which  he  prepares  two  collodions, 
which  are  mixed  for  use  in  varying  proportions. 

The  potassio-cadmium  iodide  is  made  as  follows :  332  parts 
of  iodide  of  potassium  and  366  parts  of  iodide  of  cadmium 
are  dissolved  in  the  smallest  possible  quantity  of  distilled 
water,  and  evaporated  to  dryness  by  gentle  heat,  and  bottled 
for  use. 

The  ammonio-cadmium  bromide  is  prepared  by  taking  196 
parts  of  bromide  of  ammonium  and  272  parts  of  bromide 


THE    COLLODION    PROCESS,    WET-PLATES.  55 

of  cadmium  and  treating  them  as  in  the  preparation  of  the 
double  iodide. 

The  iodized  collodion  is  made  up  as  follows : 

Double  iodide     6    grains 

Ether •..   Jounce 

Alcohol i  ounce 

Pyroxyline 2    grains 

To  make  the  bromized  collodion  take 

Double  bromide 10  grains 

Alcohol 3  drams 

Ether    5  drams 

Pyroxyline 2  grains 

For  special  use  these  collodions  are  mixed  in  the  following 
proportions : 

For  interiors  and  dimly  lighted  subjects,  two  parts  iodized 
to  one  part  bromized. 

For  quick  exposures,  three  parts  iodized  to  one  part  bromized. 
For  copying  and  process  work,  five  parts  iodized  to  one 
part  bromized. 

Mr.  Carbutt  states  that  this  collodion  should  be  allowed  to 
ripen  for  six  or  eight  weeks  before  it  is  used.  If  a  few  drops 
of  tincture  of  iodine  are  added,  it  will  be  in  good  working  or- 
der in  a  few  days. 

DR.  VOGEL'S  COLLODION. 

Iodide  of  cadmium 1    part 

Iodide  of  sodium i  part 

Bromide  of  ammonium i  part 

Alcohol 80    parts 

After  filtration  one  part,  by  measure,  of  the  filtrate  is 
added  to  three  parts,  by  measure,  of  -plain  collodion,  contain- 
ing two  per  cent,  of  pyroxyline.  The  mixture  may  be  used 

after  three  days. 

EQUIVALENT  COLLODION. 

a.  Iodide  of  cadmium 18  parts 

Alcohol 270  parts 

b.  Bromide  of  cadmium 17  parts 

Alcohol 270  parts 

Two  measured  parts  of  a  are  added  to  one  measured  part 
of  b,  and  nine  measured  parts  of  plain  collodion,  containing 
two  per  cent,  of  pyroxyline. 


56 


THE   PHOTOGRAPHIC   NEGATIVE. 


This  collodion  will  keep  for  years. 

Care  of  the  Collodion. — The  proper  care  of  the  collodion  is 
a  matter  of  great  importance  to  the  photographer  who  wishes 
to  secure  uniformly  good  results. 

The  chemical  changes  which  a  salted  collodion  undergoes  are 
manifested  by  a  change  of  color  to  yellow  and  red,  and  by  a 
decrease  of  sensitiveness.  Red  collodion  may  be  corrected  by 
the  addition  of  cadmium  collodion,  which  remains  white  for 
months. 

A  collodion  which  has  a  tendency  to  turn  red  should  be 
mixed  only  as  wanted  for  use,  the  plain  collodion  and  the 
iodizer  being  kept  in  separate  bottles. 

The  collodion  also  becomes  thick  by  the  evaporation  of  the 
solvents.  When  it  becomes  too  thick  to  flow  well  it  must  be 
thinned  down  by  the  addition  of  a  sufficient  quantity  of  alcohol 
and  ether  in  the  proportions  of  three  to  five. 

When  the  excess  of  collodion  is  drained  from  the  plate  into 
the  stock  bottle  it  gradually  becomes  filled  with  dust, giving 
rise  to  spots  on  the  plates.  This  evil  may  be  avoided  by  drain- 
ing the  excess  into  a  separate  bottle.  After  settling  for  a  week 
the  clear  liquid  can  be  decanted  off  and  used  for  coating. 

The  neck  of  the  stock-bottle  should  be 
kept  covered  with  a  bell  glass,  and  the  stop- 
per should  be  left  out  as  little  as  possible  to 
prevent  evaporation. 

Filtering  Collodion. — Many  collodions  set- 
tle so  slowly  as  to  require  a  tedious  length  of 
time  to  render  them  fit  for  use  unless  filtered. 
Fig.  16  shows  a  collodion  filter.  A  is  a 
glass  funnel  fitting  closely  into  the  neck  of 
the  bottle,  and  closed  by  the  glass  stopper  B 
to  prevent  the  evaporation  of  the  collodion. 
C  is  a  piece  of  glass  tubing,  around  which 

^^^ *S  washed  cotton   is  loosely  packed,    through 

FIG.  16.  which  the  collodion  slowly  filters. 

The  Sensitizing  £ath—The  office  of  the  bath  is  to  make 
the  collodion  film  sensitive  by  changing  the  metallic  iodides 
and  bromides  into  iodide  and  bromide  of  silver. 


THE    COLLODION    PROCESS,    WET-PLATES.  57 

The  utmost  care  and  cleanliness  must  be  exercised  in  the 
preparation  of  the  bath,  and  a  generous  amount  of  it  should 
be  made  up.  It  is  customary  to  add  a  trace  of  iodide  of  potas- 
sium to  prevent  the  bath  eating  away  the  film,  owing  to  the 
solubility  of  iodide  of  silver,  in  a  solution  of  nitrate  of  sil- 
ver. Dilute  nitric  acid  is  also  added  sparingly  when  the  plates 
show  signs  of  veiling.  Other  additions  are  sometimes  refcom- 
mended,  but  their  utility  is  doubtful. 

The  strength  of  the  bath  varies  somewhat  according  to  the 
nature  of  the  work  in  hand ;  from  35  to  50  grains  of  silver  to 
the  ounce  may  be  taken  as  the  limits  in  either  direction. 

Dr.  Yogel  recommends  the  following: 

Nitrate  of  silver  (neutral) 100  parts 

Distilled  water 1000  parts 

To  which  are  added  25  parts  of  1  per  cent,  aqueous  solution 
of  iodide  of  potassium.  If  the  bath  gives  veiled  images,  a  20 
per  cent,  aqueous  solution  of  nitric  acid  is  added  drop  by  drop 
until  a  trial  plate  developes  free  from  fog. 

Hardwich  recommends  the  following  baths:  . 

FOR  BROMO-IODIZED  COLLODION. 

Nitrate  of  silver 35  grains 

Distilled  water 1  ounce 

The  required  quantity  of  solution  is  made  up  and  iodized  by 
the  addition  of  a  few  grains  of  iodide  of  potassium. 

If  the  bath  shows  a  neutral  or  alkaline  reaction  acidify  with 
dilute  nitrate  acid  until  blue  litmus  changes  slightly  to  red. 

FOR  IODIZED  COLLODION. 

Nitrate  of  silver 30  grains 

Distilled  water 1  ounce 

The  bath  is  iodized  as  before,  and,  if  necessary,  made  acid  by 
the  addition  of  acetic  acid. 

Great  care  must  be  taken  when  acidulating  the  nitrate  bath 
not  to  add  too  much  acid,  which  diminishes  the  sensitiveness 
of  the  film  and  gives  weak  images.  The  proper  way  is  to 
add  only  a  few  drops  at  a  time,  and  to  sensitize,  expose,  and 
develop  a  trial  plate  after  each  addition  until  the  image  shows 
no  deposit  of  silver  in  the  deepest  shadows,  i.  <?.,  until  it  is 
free  from  fog. 


58  .  THE    PHOTOGRAPHIC   NEGATIVE. 

To  correct  a  bath  which  is  too  acid  the  best  plan  is  to  add 
by  degrees  some  non-acidulated  nitrate  solution  of  the  same 
strength,  testing  with  trial  plates  between  each  addition. 

Management  of  the  Bath. — Collodion  plates  sensitized  in 
a  freshly  made  bath  generally,  give  clear  and  brilliant  neg- 
atives, but  by  constant  use  the  bath  undergoes  a  change;  it 
becomes  charged  with  alcohol  and  ether,  with  the  nitrates  of 
potassium,  ammonia,  cadmium,  etc.,  the  products  of  double 
decomposition,  with  various  substances  derived  from  the 
pyroxyline,  with  dust  and  impurities  from  various  sources.  In 
this  condition  the  bath  will  not  produce  good  results;  it  must 
be  purified. 

The  insoluble  substances  contained  in  an  old  bath  are  easily 
removed  by  filtration.  The  soluble  organic  substances  are  de- 
stroyed by  exposing  the  bath  to  sunlight.  Under  the  action  of 
light  the  greater  portion  of  the  organic  matter  is  burnt  up,  as 
it  were,  by  the  nitrate  of  silver,  which  is  at  the  same  time  re- 
duced and  a  slight  trace  of  nitric  acid  is  given  off  which  aids 
the  production  of  pure  and  brilliant  negatives.  The  bath 
should  be  "  sunned  "  occasionally  when  not  in  use. 

With  long  use  the  bath  becomes  so  charged  with  alcohol  and 
ether  as  to  be  unfit  for  use  until  these  have  been  removed  by 
evaporation.  For  this  purpose  the  bath  may  be  poured  out 
into  a  large  tray  and  left  uncovered  for  some  hours,  when  most 
of  the  alcohol  and  ether  will  have  evaporated.  The  process 
may  be  hastened  by  the  application  of  heat  When  this 
method  is  adopted  the  bath  after  evaporation  must  be  made 
up  to  its  original  volume  by  the  addition  of  distilled 
water.  If  turbidity  is  produced  by  this  addition,  the  bath  is 
filtered,  and  acetic  acid  added  drop  by  drop,  until  a  trial  plate 
gives  a  perfectly  clear  negative. 

When  the  volume  of  the  bath  has  become  very  much  reduced, 
it  may  be  increased  by  making  up  a  new  bath,  observing  the 
following  precaution  :  To  the  old  bath  sufficient  distilled  water 
is  added  to  bring  it  up  to  the  volume  desired.  This  addition  pro- 
duces a  yellowish  discoloration,  due  to  the  precipitation  of 
iodide  of  silver ;  this  is  removed  by  filtration,  after  which  suffi- 
cient nitrate  of  silver,  in  crystals,  is  added  to  bring  the  bath  up 
to  the  proper  strength. 


THE    COLLODION    PROCESS,    WET-PLATES.  59 

If  these  simple  precautions  be  taken  no  trouble  need  be 
feared  from  the  silver  bath,  and  they  are  all  that  are  required. 

Testing  the  Strength  of  the  Silver  Bath. — An  approximately 
correct  determination  of  the  strength  of  the  bath  can  be  arrived 
at  by  the  use  of  the  argentometer,  an  instrument  graduated  to 
register  grains  of  silver  to  the  ounce  of  water. 

The  accuracy  of  this  test  is  greatly  impaired  by  the  presence 
of  foreign  matter  in  the  solution.  Since  these  are  nearly  al- 
ways present  in  the  sensitizing  bath,  the  chloride  of  sodium 
test  should  be  applied  when  accurate  knowledge  of  the  exact 
strength  is  necessary  or  desirable.  Hardwich  gives  the  follow- 
ing simple  method  of  applying  this  test : 

Pure  crystallized  chloride  of  sodium  is  dried  by  heat,  to 
eliminate  the  water  of  crystalization,  and  dissolved  in  distilled 
water  in  the  proportion  of  eight  and  one-half  drams  to  six  fluid 
ounces.  This  forms  a  standard  solution,  each  dram  of  which 
will  precipitate  half  a  grain  of  silver. 

One  dram  of  the  bath  is  accurately  measured  out  in  a  minim 
graduate  and  placed  in  a  two-ounce  stoppered  phial,  the  gradu- 
ate is  rinsed  out  with  a  dram  of  distilled  water,  which  is  added 
to  the  dram  of  bath.  A  little  bichromate  of  potash  is  then 
added  to  the  contents  of  the  phial ;  its  effect  is  to  form  a  deep 
red  precipitate  of  chromate  of  silver. 

Two  or  three  drams  of  the  standard  salt  solution  are  next 
placed  in  a  graduate  and  added  to  the  contents  of  the  phial,  in 
the  proportion  of  one  dram  for  every  four  grains  of  nitrate 
known  to  have  been  present.  The  contents  of  the  phial  are 
then  well  shaken,  and  then  examined  to  note  if  the  red  colora- 
tion shows  any  lessening  of  tint.  Further  additions  of  the  salt 
solution  are  added,  fifteen  drops  at  a  time,  until  the  red  colora- 
tion disappears,  owing  to  the  decomposition  of  the  red  chromate 
into  the  white  chloride.  The  volume  of  salt  solution  used  is 
then  determined,  when  a  simple  calculation  will  give  the  num- 
ber of  grains  of  silver  in  the  original  dram. 

The  following  example  will  make  the  method  plain  :  In  case 
the  bath  is  thought  to  contain  about  20  grains  to  the  ounce,  then 
one  dram  will  contain  two  and  one-half  grains ;  half  a  dram  of 
the  salt  solution  is  added  and  the  whole  well  shaken,  subsequent 


60  THE    PHOTOGRAPHIC   NEGATIVE. 

additions  must  be  made  more  cautiously,  a  few  drops  at  a  time, 
followed  by  vigorous  shaking.  If  it  is  found  that  40  drops  of 
the  salt  solution  were  required  to  produce  the  change  of  color, 
the  number  of  grains  of  silver  in  the  tested  dram  was  evidently 
•£$  or  f  of  4  =  2f  grains  or  21^-  grains  to  the  ounce. 

If  pure  chloride  of  sodium  can  not  be  obtained,  ordinary 
chloride  of  ammonium  may  be  substituted  in  the  proportion  of 
Tf  grains  of  the  chloride  to  6  ounces  of  water. 

Development. — A  solution  of  sulphate  of  iron  is  generally 
employed  as  a  developer  for  the  negative.  This  solution  has 
the  property  of  precipitating  silver  from  its  solution  as  a  fine 
metallic  powder.  The  same  precipitate  is  formed  when  a  solu- 
tion of  iron  is  poured  over  a  collodion  plate  still  wet  from  the 
silver  bath.  The  formation  of  the  precipitate  is,  however,  con- 
fined to  those  parts  of  the  plate  which  have  been  acted  upon 
by  light,  and  in  this  way  the  image  is  built  up. 

To  prevent  the  too  rapid  formation  of  the  precipitate  a  di- 
lute and  acidulated  solution  is  used. 

For  pictures  with  half  tones,  portraits,  landscapes,  etc.,  Dr. 
Vogel  recommends  the  following  developer : 

Sulphate  of  iron 3  parts 

Glacial  acetic  acid 3  parts 

Water 100  parts 

When  an  old  nitrate  bath  is  used  two  parts  of  alcohol  should 
be  added  to  the  developer. 

A  typical  American  developer  is 

Sulphate  of  iron .   1  ounce 

Water ,..16  ounces 

Acetic  acid 1  ounce 

For  soft  effects  in  portraiture  the  following  is  recommended : 

Sulphate  of  iron  and  ammonia 1%  ounces 

Acetic  acid 1  ounce 

Water 16  ounces 

The  sulphate  of  iron  solution  must  be  freshly  mixed  every 
two  or  three  days.  The  sulphate  of  ammonia  and  iron  modifi- 
cation will  keep  for  a  long  time. 

Intensification. — In  many  cases  the  developed  image  is  too 
weak  to  be  printed  from  with  good  results ;  it  must  then 


;oo 
be 


THE   COLLODION   PROCESS,    WET-PLATES.  61 

strengthened  by  the  process  called  intensification.     This  is 
effected  by  pouring  on  the  plate  a  silver  solution  combined  with 
some  reducing  agent,  usually  pyrogallic  acid  or  sulphate  of  iron. 
The  following  formulae  will  produce  good  results : 

a.  Pyrogallic  acid 1  part 

Alcohol 10  parts 

b.  Nitrate  of  silver 2  parts 

Citric  acid 3  parts 

Water ' 100  parts 

This  solution  will  keep  for  two  weeks. 

For  use  dilute  a  small  quantity  of  a  with  twenty-five  parts 
of  water  and  mix  with  an  equal  volume  of  b. 

In  summer  four  parts  of  citric  acid  may  be  used  instead  of 
three,  to  retard  the  action  of  the  intensitier.  In  winter  it  will 
be  well  to  reduce  the  proportion  to  one  part.  The  plate  must 
be  well  washed  before  the  solution  is  applied. 

The  iron  intensifier  is  as  follows  : 

a.  Sulphate  of  iron 3  parts 

Glacial  acetic  acid 3  parts 

Water 100  parts 

b.  Nitrate  of  silver 2  parts 

Citric  acid 3  parts 

Alcohol 2  to  3  parts 

Water 100  parts 

Equal  volumes  of  a  and  b  are  taken  to  form  the  intensifier. 
The  advantage  of  this  method  is  that  the  plate  need  not  be 
washed  after  development.  It  is  much  better  not  to  intensify, 
but  to  give  the  proper  density  to  the  negative  by  development. 

Fixing. — The  object  of  the  fixing-bath  is  to  remove  the  un- 
reduced iodide  and  bromide  of  silver,  and  so  protect  the  pic- 
ture from  further  changes  through  the  action  of  light.  For 
this  purpose  either  a  1  to  5  solution  of  hyposulphite  of  soda 
or  a  1  to  20  solution  of  cyanide  of  potassium  is  employed. 

The  only  objection  to  the  use  of  hyposulphite  of  soda  as  a 
fixing  agent  is  the  prolonged  washing  necessary  to  remove  it 
from  the  film. 

Cyanide  of  potassium  is  more  easily  washed  away,  but  it  is 
a  deadly  poison,  and  attacks  the  half-tones  unless  quickly  re- 
moved by  washing. 


62  THE  PHOTOGRAPHIC  NEGATIVE. 

PRACTICAL  MANIPULATIONS. 

Collodionising. — The  plates  to  be  collodionized  must  have 
been  previously  cleaned,  as  described  in  Chapter  IY. 

To  collodionize,  the  plate  is  held  between  the  thumb  and 
fingers  of  the  left  hand  at  the  left  lower  corner,  and  brought 
into  a  horizontal  position.  The  mouth  of  the  collodion  bottle 
is  brought  near  the  surface  of  the  plate  and  sufficient  collodion 
is  poured  on  to  cover  two-thirds  of  the  surface.  The  plate  is 
then  gently  rocked,  to  secure  an  even  coating  over  the  entire 
surface,  and  the  surplus  is  drained  from  the  lower  right-hand 
corner  into  a  separate  bottle,  to  be  filtered  before  being  added 
to  the  stock  collodion. 

As  soon  as  the  surface  has  become  tacky,  the  plate  is  placed 
on  the  glass  dipper  and  kept  in  a  horizontal  position  until  the 
lower  corner  has  dried  so  that  the  collodion  will  tear.  It  is 
then  ready  for 

Sensitizing. — The  plate  is  lowered  slowly  and  without  stop- 
page into  the  silver  solution  contained  in  a  vertical  glass  bath. 
Any  interruption  in  this  operation  will  produce  lines  visible 
in  the  finished  negative. 

At  first  the  alcoholic  film  repels  the  bath,  which  will  run  off 
the  plate  in  greasy  lines,  if  it  is  removed  shortly  after  im- 
mersion. 

The  plate  must  remain  in  the  bath  until  these  greasy  lines 
disappear,  being  gently  moved  up  and  down.  It  is  then  placed 
in  the  same  position  on  blotting-paper,  with  its  top  against  the 
wall,  and  allowed  to  drain,  after  which  it  is  placed  in  the 
holder,  care  being  taken  that  the  edge  of  the  plate  which  left 
the  bath  last  occupies  the  lower  end  of  the  holder. 

Sensitizing  in  Trays. — The  plates  may  be  sensitized  in 
trays.  This  method  requires  less  silver  solution  than  that 
with  the  vertical  bath,  but  care  must  be  taken  to  remove  the 
scum  which  forms  on  the  surface  with  a  piece  of  clean  paper. 

One  end  of  the  tray  is  raised  slightly  higher  than  the  other, 
and  a  sufficient  quantity  of  the  silver  solution  is  filtered  into  it 
to  cover  rather  more  than  half  of  the  bottom,  one  end  of  the 
plate  is  placed  in  the  bath,  and  the  plate  is  then  lowered,  face 
down,  by  means  of  a  horn  or  silver  hook.  The  liquid  flows 


THE    COLLODION    PROCESS,    WET-PLATES.  63 

between  the  glass  and  the  bottom  of  the  tray  by  capillary 
attraction  and  so  covers  the  whole  film.  This  method  is 
recommended  for  experimental  work  on  a  small  scale,  as 
being  more  economical. 

Another  method  is  to  lower  the  plate  film  up  into  the  solu- 
tion placed  in  a  tray  having  a  tank  at  one  end. 

The  tray  is  placed  in  a  vertical  position,  the  plate  is  placed 
in  the  tray,  which  is  then  rapidly  lowered. 

Exposure. — No  definite  instructions  can  be  given  as  to  the 
proper  time  of  exposure,  which  depends  on  the  chemical  inten- 
sity of  the  light,  the  brightness  of  the  object  to  be  photo- 
graphed, and  the  size  of  the  diaphragm. 

The  plate-holder  must  be  kept  always  in  the  vertical  posi- 
tion, to  prevent  the  running  back  over  the  plate  of  the  silver 
solution  which  collects  at  the  bottom. 

It  is  essential  that  all  the  operations  at  the  camera  be  done     ^f^ 
rapidly,  as  the  plates  will  keep  moist  only  a  short  time.  ^-7— . s 

development. — The  plate,  after  exposure,  is  taken  into  the 
dark-room,  always  being  kept  in  its  original  vertical  position. 
It  is  removed  from  the  plate-holder  inclined  towards  the  edge 
which  was  lowest  in  the  holder. 

The  developer  is  then  poured  on  the  upper  part  of  the  plate 
in  such  a  way  as  to  cover  the  whole  plate  with  one  sweep. 
This  must  be  done  gently  and  with  care,  to  avoid  unequal  re- 
duction of  the  silver. 

The  image  now  becomes  visible,  the  high-lights  appearing 
first,  and  gradually  gains  in  detail  and  density.  The  operation 
must  be  wTatched  with  great  care,  and  fresh  additions  of  the 
developer  made  when  necessary,  the  plate  being  kept  in  con- 
stant but  not  violent  motion. 

If,  after  long-continued  development,  the  details  in  the 
shadows  do  not  appear,  the  plate  was  under-exposed  and  is 
worthless. 

If,  on  the  contrary,  all  the  details  appear,  but  the  image  is 
wanting  in  contrasts,  the  exposure  was  too  long,  and  the  plate 
must  be  intensified.  When  fully  developed,  the  plate  is 
washed,  and  if  not  sufficiently  dense,  it  is  intensified  before 
fixing. 


64  THE    PHOTOGRAPHIC   NEGATIVE. 

Intensification. — The  intensifier,  mixed  as  directed  on  page 
61,  is  poured  over  the  plate  and  allowed  to  act  until  sufficient 
density  is  reached ;  it  is  then  thoroughly  washed  and  fixed. 
The  intensifier  must  be  rejected  as  soon  as  it  becomes  turbid. 
Intensification  may  be  done  after  fixing. 

Fixing. — The  plate  is  immersed  in  either  of  the  fixing  solu- 
tions given  on  page  61,  until  the  last  trace  of  iodide  of  silver 
has  disappeared.  It  is  then  well  washed  and  dried. 

Varnishing. — The  instructions  given  on  page  31  may  be 
followed  here. 

Defects. — The  most  common  defects  in  collodion  negatives 
are  the  following : 

Fog:  due,  a,  to  dirty  plates;  2»,  to  want  of  acid  in  the  de- 
veloper ;  c,  to  over-exposure ;  d,  to  an  alkaline  bath  solution  ; 
e,  to  improper  exposure  to  white  light ;  /,  to  vapors  in  the 
developing-room. 

Weak  images :  due,  a,  to  a  poor  collodion ;  5,  to  a  weak 
sensitizing  solution  ;  <?,  to  a  bath  charged  with  organic  matter ; 
<7,  to  bad  lighting  of  the  subject ;  e,  to  an  over-strong  devel- 
oper. 

Pin-holes :  due,  #,  to  dust  on  the  plate ;  b,  to  an  over  or 
under-iodized  bath. 

Black  specks :  due,  #,  to  dust  in  the  camera,  slide,  dark- 
room, or  collodion. 

Comet-like  spots :  due  to  undissolved  particles  of  pyroxyline 
in  the  collodion. 

Transparent  spots :  due  to  dust  in  the  collodion. 

Scum  on  the  film:  a,  the  plate  has  been  kept  too  long  out 
of  the  bath  ;  or,  £,  the  developer  was  too  strong. 

Wavy  lines  on  the  film :  either  the  collodion  contains  too 
much  iodide  or  alcohol,  or  the  pyroxyline  is  too  strong, 

Transparent  markings :  due,  #,  to  unequal  sensitizing,  or, 
b,  to  the  developer  refusing  to  flow. 

Blurring  of  the  image :  due  to  reflections  from  the  back  of 
the  plate ;  it  may  be  diminished  by  coating  the  back  of  the 
plate  with  some  non- actinic  color,  such  as  sienna,  mixed  in 
gum-water. 


CHAPTER  VII. 

THE  COLLODION  PROCESS.  DRY  PLATES. 

HARDLY  had  the  wet  collodion  process  established  itself  in 
public  favor  before  attempts  were  made  to  make  it 
more  suitable  for  the  landscape  photographer  by  giving  him 
dry  collodion  plates,  of  fair  keeping  qualities.  Up  to  the  time 
when  the  gelatine  process  was  introduced,  the  zeal  of  experi- 
menters knew  no  flagging,  and  many  valuable  dry  plate  proc- 
esses were  elaborated  by  skillful  workers.  The  fact  that  all 
of  these  processes  have  been  almost  entirely  superseded  by  the 
gelatine  dry  plate,  does  not  make  a  description  of  some  of  the 
best  unnecessary  or  out  of  place.  They  have  a  value  still,  no- 
tably for  the  economical  production  of  lantern  slides  on  a  large 
scale,  while  the  Taupinot  process  gives  results  extremely  diffi- 
cult to  be  equalled  by  the  more  modern  method. 

Success  in  these  processes  depends  on  the  strict  observance 
of  the  following  principles  : 

Firm  adherence  of  the  sensitive  surface. 

Permeability  of  the  collodion  film. 

The  use  of  a  large  proportion  of  bromide. 

Complete  elimination  of  all  the  free  nitrate  of  silver  by 
copious  washing. 

The  use  of  a  preserver  to  give  keeping  qualities  to  the  plates. 

The  use  of  alkaline,  or  other  similar  developers  to  reduce  the 
bromide  of  silver  to  the  metallic  state. 

The  strict  observance  of  all  the  details  given  under  each  of 
the  processes  described,  will  enable  the  operator  to  meet  all 
these  conditions  and  make  success  certain. 

TaupinoCs  Collodio-Albumen  Process. — This  method  gives 
negatives  of  fine  detail  and  exquisite  delicacy.  The  manipu- 
lations are  not  over  difficult,  and  the  plates  are  fairly  sensitive. 


66  THE   PHOTOGRAPHIC   NEGATIVE. 

The  manipulations  may  be  thus  summarized  :  The  plates, 
previously  polished  with  French  chalk,  or  flowed  over  with  a 
thin  film  of  albumen,  as  described  in  Chapter  V.,  are  collodion- 
ized  as  usual  with  any  of  the  collodions  given  in  the  previous 
chapter.  They  are  then  sensitized  in  the  nitrate  bath,  well 
washed,  and  given  a  coating  of  iodized  or  iodo-bromized  albu- 
men, which  destroys  the  sensitiveness  conferred  by  the  silver 
bath.  When  dry  the  plates  will  present  a  brilliant,  opalescent 
appearance,  and  can  be  preserved  indefinitely.  When  wanted 
for  use  they  are  sensitized  in  an  acidulated  silver  bath, thoroughly 
washed,  and  then  flowed  with  a  solution  of  gallic  acid  to  pre- 
serve them.  In  this  condition  they  will  retain  their  good  qual- 
ities for  two  weeks. 

Manipulations. — Collodionize  as  usual ;  stand  the  plate  on 
one  corner  on  two  or  three  thicknesses  of  blotting  paper,  sup- 
porting it  against  the  wall,  face  down.  After  a  minute's  stand- 
ing, sensitize  as  usual  on  the  following  bath  : 

Water 3J4  ounces 

Nitrate  of  silver 100  to  125  grains 

Nitric  acid ...  .3  or  4  drops 

This  bath  should  be  filtered  occasionally,  kept  acid,  and 
stood  in  the  sun  when  not  in  use. 

After  being  sensitized  the  plate  is  washed  in  three  or  four 
changes  of  pure  water,  and  then  allowed  to  drain,  one  of  the 
lower  corners  being  supported  in  a  beaker,  the  upper  corner 
resting  against  the  wall,  the  film  side  being  uppermost. 

After  being  well  drained  the  plate  is  coated  with  the  follow- 
ing albumen  solution : 

Albumen 3%  ounces 

Bromide  of  ammonium 3%  grains 

Iodide  of  ammonium 15  grains 

The  albumen  must  first  be  beaten  and  treated  as  described 
on  page  40. 

A  more  simple  method  is  that  of  Mr.  Ackland.  Place  the 
whites  of  several  eggs  in  a  large  graduate,  and  for  each  three 
and  one-half  ounces  of  albumen  add  two  drams  of  a  1  to  10  solu- 
tion of  glacial  acetic  acid  ;  gently  stir  the  mixture  with  a  glass 
rod  until  the  albumen  becomes  fluid,  then  allow  it  to  stand  for 


THE    COLLODION   PROCESS.       DKY   PLATES.  67 

two  hours ;  then  decant  the  clear  portion  into  a  funnel,  having  a 
piece  of  sponge  in  the  tube  ;  when  this  has  filtered  through,  pour 
in  the  balance  of  the  liquid.  Before  using,  the  albumen  must 
be  again  filtered  through  filter  paper,  avoiding  air  bubbles  by 
bringing  the  tube  of  the  filter  in  contact  with  the  side  of  the 
glass,  or  by  the  method  of  upward  filtration  before  described. 

This  solution  is  flowed  over  the  plate  like  collodion,  and  the 
plate  is  drained  as  described  above.  When  well  drained  it  is 
dried  in  the  drying  box,  or  spontaneously  in  the  open  air,  sup- 
ported vertically,  so  that  no  part  of  the  film  is  in  contact  with 
any  foreign  substance. 

When  dry  the  plates,  which  are  insensitive,  will  keep  inde- 
finitely. 

To  sensitize  they  are  immersed  in  the  following  bath  : 

Water 3^£  ounces 

Nitrate  of  silver 100     grains 

Glacial  acetic  acid 2     drams 

Each  plate  remains  in  the  bath  one-half  a  minute  ;  it  is  then 
washed  in  four  changes  of  distilled  or  filtered  water  and  the 
gallic  acid  preservative  flowed  over  it,  (water,  thirty-five 
ounces ;  gallic  acid,  seventy-five  grains);  this  is  applied  twice, 
and  the  plate  is  then  dried.  Plates  prepared  in  this  way  will 
retain  their  good  qualities  for  two  weeks. 

Exposure  and  Development. — The  time  of  exposure  varies 
from  four  to  ten  minutes,  according  to  circumstances. 

The  image  is  developed  with  either  of  the  following  de- 
velopers : 

Water. : 35  ounces 

Gallic  acid 45  grains 

Pyrogallic  acid 45  grains 

Glacial  acetic  acid 4  drams 

The  plate  is  placed  in  a  tray  and  sufficient  of  this  solution 
poured  over  it  to  cover  it.  While  this  is  acting  one  to  two 
drams  of  a  one  to  twenty-five  solution  of  nitrate  of  silver  are 
placed  in  a  graduate,  and  the  contents  of  the  tray  poured  into 
it.  The  liquid  is  then  returned  to  the  tray  ;  the  image  will 
soon  appear  and  rapidly  gain  in  detail  and  density. 


68  THE    PHOTOGRAPHIC    NEGATIVE. 

The  following  developer  will  generally  be  found  the  best : 

a.  Water 35  ounces 

Carbonate  of  ammonia 155  grains 

Bromide  of  potassium 1  grain 

b.  Water 35  ounces 

Pyrogallic  acid 155  grains 

Mix  a  and  b  in  equal  parts  and  pour  over  the  plate  pre- 
viously soaked  in  distilled  water.  The  image  will  appear 
almost  immediately,  and  should  show  no  signs  of  fog.  If  fog 
appears,  due  to  over-exposure,  add  a  few  drops  of  a  one  to  ten 
solution  of  bromide  of  potassium. 

The  action  of  this  developer  should  be  stopped  before  all 
the  details  in  the  shadows  are  visible,  and  the  development 
completed  in  the  gallic  and  pyrogallic  solution  given  above. 
The  plate  is  immersed  in  this  for  a  moment  until  the  acetic 
acid  has  removed  all  traces  of  alkalinity ;  it  is  then  removed 
from  the  developer,  to  which  a  few  drops  of  a  one  to  twenty- 
five  nitrate  of  silver  solution  are  added,  and  the  plate  returned 
to  the  tray.  Development  is  soon  completed ;  the  plate  is  then 
washed  and  fixed  in  a  one  to  five  hyposulphite  of  soda  solu- 
tion, after  which  it  is  washed,  dried,  and  varnished  as  usual. 

Boiwin's  Process. — This  method  gives  negatives  of  the  very 
highest  grade,  free  from  danger  of  frilling,  full  of  detail  in 
the  shadows,  and  with  the  distances  properly  rendered.  The 
sensitized  plates  retain  their  good  qualities  for  months. 

Manipulations. — The  plates  are  first  well  cleaned,  and  then 
without  any  previous  coating  they  are  collodionized  as  usual 
with  the  following  collodion  : 

Ether 17  drams 

Alcohol 11  drams 

Nitrate  of  silver 15  grains 

Pyroxyline 15  grains 

The  nitrate  of  silver  is  placed  in  a  glass-stoppered  bottle, 
one  or  two  drops  of  distilled  water  are  poured  over  it,  and 
when  the  silver  is  dissolved,  or  nearly  so,  the  alcohol  is  added, 
and  the  bottle  shaken  until  solution  is  complete;  then  the 
ether  and  the  pyroxyline  are  added,  and  the  bottle  again 
shaken.  The  resulting  collodion  must  be  allowed  to  ripen  for 


THE    COLLODION    PROCESS.       DRY    PLATES.  69 

twenty-four  hours  before  being  used.  If  found  too  thick  to 
flow  well,  sufficient  alcohol  and  ether  in  the  proportions  of 
four  to  six  must  be  added  to  thin  it  down.  The  collodion 
will  keep  indefinitely  in  a  dry,  dark  place. 

As  soon  as  the  collodion  is  set,  the  plate  is  immersed  with- 
out stoppage  in  the  following  bath  : 

Distilled  water 3%  ounces 

Iodide  of  cadmium 30     grains 

Iodide  of  ammonium 15     grains 

Iodide  of  potassium 30     grains 

Bromide  of  potassium 20     grains 

As  soon  as  all  traces  of  oiliness  have  disappeared,  the  plate 
is  taken  from  the  bath  and  washed  in  four  changes  of  pure 
rain  water,  aiid  then  inclined  against  the  wall,  face  down,  to 
drain,  blotting  paper  being  placed  under  the  lower  edge. 

The  next  step  is  to  cover  the  film  with  an  albumen  solution 
prepared  as  follows  : 

Whites  of  six  eggs  beaten  to  a  froth 

Distilled  water 2  ounces 

Dextrine 90  grains 

Glucose 90  grains 

Iodide  of  potassium 22  grains 

Bromide  of  potassium .17  grains 

Iodide  of  ammonium 22  grains 

Bromide  of  ammonium 7  grains 

Iodide  in  pellets. 5  grains 

The  dextrine  and  the  glucose  are  first  dissolved  in  the  water 
by  heat,  the  water  lost  by  evaporation  is  replaced ;  the  salts 
are  then  dissolved,  and  the  solution  is  added  to  the  albumen 
and  whole  well  shaken  ;  a  few  drops  of  ammonia  are  then 
added  and  the  solution  is  allowed  to  stand  some  hours  before 
being  used.  It  is  then  filtered  and  flowed  over  the  still  moist 
plate ;  two  thin  coatings  are  given  to  the  plate,  which  is  then 
dried  at  a  temperature  of  about  70  deg.  The  plates  will 
keep  indefinitely. 

Sensitizing  is  effected  by  plunging  the  plates  rapidly  and 
without  stoppage  in  the  following  bath  : 

Distilled  water 3J^  ounces 

Nitrate  of  silver 95      grains 

Glacial  acetic  acid 2^£  drams 

Iodide  of  potassium 10      grains 


70  THE    PHOTOGRAPHIC   NEGATIVE. 

The  plates  are  immersed  for  one  minute,  and  then  washed  in 
three  or  four  changes  of  distilled  water.  The  first  wash  water 
being  preserved  in  a  well-corked  bottle  for  use  in  develop- 
ment as  explained  later  on,  finishing  up  with  a  good  washing 
Tinder  a  rose,  or  with  a  pipette.  They  are  then  dried  in  the 
dark. 

M.  Boivin  claims  that  these  plates  will  retain  all  their  good 
qualities  for  six  months,  and  the  author  can  certify  to  the  good 
results  obtained  from  them  with  exposures  varying  from  one 
to  five  minutes. 

Development. — The  exposed  plate  is  immersed  for  a  few 
minutes  in  the  wash  water  preserved  for  this  purpose  as 
directed  above  ;  it  is  then  immersed  in  a  bath  prepared  as 
follows : 

Solution  of  gallic  acid  (1  to  250) 3%  ounces 

Rain  water 3%  ounces 

Solution  of  acetate  of  soda  (1  to  20) 4      ounces 

If  the  details  develop  too  slowly  add  a  few  drops  of  a  ten- 
gram  solution  of  nitrate  of  silver. 

When  the  details  are  well  out  strengthen  with  the  follow- 
ing: 

Distilled  water 9  ounces 

Pyrogallic  acid 15  grains 

Glacial  acetic  acid 3  to  4  drams 

If  the  negative  is  flat  and  lacks  vigor,  substitute  the  follow- 
ing: 

Distilled  water 9  ounces 

Pyrogallic  acid 15  grains 

Citric  acid 20  to  30  grains 

If  detail  is  wanting  immerse  the  plate  in  a  strong  gallic  acid 
solution  containing  a  little  nitrate  of  silver. 

Fix  in  a  saturated  solution  of  hyposulphite  of  soda. 

M.  Boivin  recommends  the  following  modifications  in  the 
preparation,  to  produce  still  greater  perfection  of  results.  They 
are  not,  however,  indispensable. 

After  sensitizing  and  washing  as  usual,  the  plates  are  im- 
mersed in  a  one  per  cent,  solution  of  bromide  of  potassium, 


THE  COLLODION  PROCESS.   DRY  PLATES.  i  1 

then  washed  and  immersed  in  a  twenty  per  cent,  solution  of 
pyro,  to  which  a  few  drops  of  acetic  acid  have  been  added. 
They  are  then  well  washed  by  pouring  water  over  them  from 
a  flask  and  dried  as  usual.  Plates  thus  prepared  seem  to  keep 
better,  are  more  sensitive  to  feeble  light,  and  yield  plucky  neg- 
atives, full  of  fine  detail  in  foliage. 

The  Tannin  Process. — The  plates  are  collodionized  with  one 
of  the  following  collodions  : 

No.  1. 

a.  Pyroxyline  (very  soluble) 61      grains 

Ether 5%  ounces 

Alcohol 2^8  ounces 

b.  Iodide  of  cadmium. 135      grains 

Iodide  of  ammonium 37^  grains 

Bromide  of  cadmium 112      grains 

Alcohol 12^  ounces 

Mix  three  parts  of  a  with  one  of  S,  and  add  enough  iodine  to 
give  a  slight  tinge  of  color. 

Sensitize  in  a  ten  per  cent,  nitrate  bath,  slightly  acidified 

with  nitric  acid. 

No.  2. 

Pyroxyline 88^  grains 

Bromide  of  cadmium 77      grains 

Bromide  of  ammonium , 20      grains 

Alcohol   538  ounces 

Ether 5%  ounces 

In  this  case  sensitize  in  a  fifteen  per  cent,  nitrate  bath. 
After  sensitizing,  wasli  well  and  flow  twice  with  the  follow- 
ing preservative : 

Distilled  water 3%  ounces 

Tannin 30  to  45      grains 

and  dry  as  usual. 

These  plates  retain  their  good  qualities  for  about  two  weeks, 
but  they  are  slow. 

Development. — The  following  developer  is  recommended : 

Carbonate  of  ammonia 75  grains 

Distilled  water 24  ounces 

Alcohol 12  ounces 

First  well  moisten  the  plate  in  a  sufficient  quantity  of  this 


72  THE    PHOTOGRAPHIC    NEGATIVE. 

solution  ;  then  pour  the  developer  into  a  graduate  and  add  a 
few"  drops  of  a  fifty  grain  alcoholic  solution  of  pyro,  and  pom- 
back  on  the  plate.  More  pyro  may  be  added  if  necessary  to 
give  density.  Fix  and  wash  as  usual. 

Sutton's  Method  for  Instantaneous  Views. — Sensitize  the 
plates  on  a  plain  bromized  collodion  containing  45  grains  of 
bromide  to  every  3^-  ounces  of  normal  collodion ;  sensitize  on  an 
eighteen  per  cent,  nitrate  bath.  After  washing  and  draining 
flow  the  plates  with  the  following  preservative  : 

Albumen 1  part 

Water 2  parts 

Glycerine 1  part 

Dry  as  usual  and  use  the  same  day. 

Develop  in  the  alkaline  bath  given  for  the  tannin  process, 
or  in  the  sulphate  of  iron  bath ;  in  the  latter  case  the  plate 
must  be  immersed  in  a  four  per  cent,  solution  of  nitrate  of 
silver  after  washing.  Fix  and  wash  as  usual. 

The  Gum  Gallic  Process, — The  process  now  to  be  described 
is  a  modification  of  that  of  Mr.  Manners  Gordon.  Plates  thus 
prepared  give  good  detail  in  foliage,  with  an  exposure  varying 
from  ten  to  sixty  seconds,  but  they  cannot  be  kept  longer  than 
four  or  five  days. 

The  plates  are  first  given  a  thin  coating  of  dilute  albumen, 
to  promote  adhesion  of  the  film  ;  they  are  then  collodionized 
with  a  collodion  containing  equal  quantities  of  the  iodides  and 
bromides  ;  sensitized  in  an  eight  per  cent,  nitrate  bath  and  well 
washed,  the  last  wash  water  containing  a  slight  trace  of  pyro- 
gallic  acid  and  a  drop  of  glacial  acetic  acid.  They  are  then 
drained  and  flowed  with  the  following  preserver,  well  filtered  : 

Water 3%  ounces 

Gum  arable  60  grains 

Glucose  or  sugar  candy 15  grains 

Develop  with  Boivin's  developer,  given  above.  Fix  and 
wash  as  usual. 


x-v 

<t£        V^ 

CHAPTER  VIII. 

COLLODION   EMULSION.    COLLODIO-BROMIDE  OF  SILVER. 

MANY  attempts  were  made  at  various  times  to  simplify  the 
collodion  process  by  manufacturing  a  collodion  containing  the 
sensitive  substances  suspended  in  a  state  of  extremely  fine 
division. 

The  first  efforts  in  this  direction  seem  to  have  been  made  as 
early  as  1853  by  M.  Gaudin,  a  French  experimenter,  but  he 
did  not  fully  work  out  the  method.  It  was  not  until  1864  that 
the  process  came  into  general  use,  owing  chiefly  to  the  publica- 
tion in  that  year  by  Messrs.  Sayce  and  Bolton  of  the  results  of 
their  experiments  with  collodio-bromide  emulsion.  During  the 
next  ten  years  many  formulae  were  published  for  preparing 
plates  by  the  new  method.  A  few  of  the  best  of  these  have 
been  selected  for  detailed  treatment,  including  the  process  of 
M.  Chardon,  which,  in  1875,  won  the  prize  offered  by  the 
French  Photographic  Society  for  the  best  set  of  formulae  for 
working  this  process. 

As  it  seems  highly  probable  that  collodion  emulsion  will  be 
increasingly  employed,  especially  for  the  production  of  trans- 
parencies, and  as  success  with  the  process  depends  upon  the 
attention  paid  to  various  details  which  are  not  of  paramount 
importance  in  the  wet  collodion  process,  it  has  been  thought 
advisable  to  give  a  few  hints  on  points  likely  to  be  neglected  by 
the  experimenter.  These  general  notes  will,  it  is  hoped,  serve 
to  clear  the  way  for  the  more  detailed  description  of  the  typi- 
cal processes  given  later  in  the  chapter. 

The  Pyroxyline. — For  washed  emulsions  it  is  better  that  the 
sample  of  pyroxyline  employed  should  not  be  that  known  as 
high  temperature  cotton.  The  most  suitable  pyroxyline  for 


74  THE  PHOTOGRAPHIC    NEGATIVE. 

this  class  of  work  is  the  somewhat  tough  or  horny  variety,  pro- 
duced when  ordinary  cotton  is  dissolved  in  a  preponderance  of 
sulphuric  acid,  at  a  temperature  varying  from  140  to  150  deg. 
The  after-washing  of  the  emulsion  seems  to  produce  a  change 
in  this  kind  of  pyroxyline,  making  it  eminently  suitable  for 
emulsion  work. 

The  Bromides. — As  a  matter  of  convenience  it  is  best  to 
use  the  bromides  of  ammonium,  cadmium,  and  zinc.  But  ow- 
ing to  the  insolubility  of  the  former  salt  in  alcohol  it  must 
be  combined  with  the  bromide  of  cadmium  to  form  the  dou- 
ble salt  of  ammonium  and  cadmium,  which  is  sufficiently  soluble 
in  alcohol  to  give  a  highly  salted  collodion. 

The  double  salt  is  easily  made  by  placing  the  proper  quanti- 
ties of  the  two  salts  in  a  mortar,  and  then  to  mix  them  inti- 
mately with  the  pestle.  The  water  of  crystallization  is  thus 
separated,  and  a  pasty  mass  is  formed,  which  is  dried  in  an 
oven  ;  when  thoroughly  dry  it  is  ready  for  use. 

Bromide  of  zinc  gives  a  richer  and  closer  film  than  either  of 
the  others,  and  is  therefore  not  so  suitable  for  slides  and  trans- 
parencies. 

Making  the  Collodion  and  Emulsion. — The  best  method  is 
to  make  up  the  plain  collodion  first,  reserving,  however,  a  part 
of  the  alcohol  to  be  used  later.  When  an  emulsion  is  to  be 
made,  the  bromides  are  placed  in  the  emulsifying  bottle  and 
the  proper  quantity  of  plain  collodion  poured  over  them,  and 
the  bottle  shaken  until  the  salts  are  dissolved.  In  this  way 
there  is  absolute  certainty  of  having  the  amount  of  bromide 
necessary  to  convert  the  silver. 

The  silver  is  to  be  dissolved  in  the  reserved  alcohol.  This 
is  a  slow  and  tedious  operation,  but  it  may  be  greatly  hastened 
by  dissolving  the  silver  in  the  smallest  possible  quantity  of  dis- 
tilled water,  and  then  adding  the  alcohol  at  its  boiling  point. 
Nitrate  of  silver  is  dissolved  in  rather  less  than  half  its  weight 
of  boiling  water.  If  then  the  required  weight  of  silver  be 
placed  in  a  test  tube,  and  half  as  many  drops  of  water  added 
as  there  were  grains  of  silver,  the  latter  may  be  dissolved  by 
holding  the  test  tube  in  the  flame  of  a  lamp  until  the  water 
boils.  The  alcohol  is  then  added  in  small  quantities,  and  the 


COLLODION    EMULSION.  75 

solution  is  re-heated  after  each  addition.  Or  if  the  alcohol  has 
been  previously  brought  near  its  boiling  point  it  may  all  be 
added  at  once  without  precipitating  the  silver.  The  silver 
solution  should  be  heated  nearly  to  boiling  before  it  is  added 
to  the  bromized  collodion  to  avoid  danger  of  crystallization. 
The  flask  is  always  to  be  washed  out  with  a  small  quantity  of 
alcohol  reserved  for  that  purpose,  and,  finally,  with  some  of 
the  emulsion  itself  to  obtain  every  trace  of  silver. 

Ripening  the  Emulsion. — This  process  is  necessary  to  the 
production  of  that  creamy  condition  which  is  essential  to  good 
results.  The  length  of  time  required  to  attain  this  creaminess 
varies  with  different  emulsions.  Those  in  which  an  excess  of 
silver  nitrate  is  present  will  be  sufficiently  ripened  in  a  few 
hours ;  while  those  in  which  the  bromide  is  in  excess  may  re- 
quire days,  and  even  weeks  to  reach  their  best  condition.  The 
ripening  process  can  always  be  hastened  by  adding  a  small 
quantity  of  an  old  emulsion  in  good  condition. 

Washing  and  Organifying. — Washing  is  a  most  important 
matter.  The  best  method  for  small  batches  is  to  pour  the 
emulsion  out  into  a  clean  dish  of  sufficient  size  to  allow  it  to 
set  in  a  thin  layer,  and  when  set  to  wash  in  many  changes  of 
water,  the  last  change  being  distilled  water.  If  it  is  proposed 
to  use  an  organifyer,  the  better  mode  of  using  is  to  allow  it  to  act 
a  quarter  of  an  hour  upon  the  set  film  before  washing  is  begun. 

For  re-dissolving  the  emulsion,  always  use  a  flask  of  double 
the  capacity  required  to  hold  the  emulsion.  This  allows  room 
for  vigorous  shaking.  The  above  method  of  working  is 
recommended  by  Mr.  Bolton,  and  it  is  a  safe  one  to  follow. 

C/iardon's  Method. 

For  the  successful  working  of  this  process,  the  two  kinds  of 
pyroxyline  described  in  Chapter  Y.  are  necessary. 

These  are  dissolved  in  separate  mixtures  of  ether  and  alco- 
hol, and  the  solution  allowed  to  settle.  The  clear  liquid  is 
then  decanted,  and  the  pyroxyline  precipitated  from  both  solu- 
tions by  pouring  the  collodion  from  a  height  in  a  fine  stream 
into  a  dish  of  pure  water,  stirring  well  during  the  pouring  and 
for  a  short  time  afterwards.  The  effect  of  this  is  to  deprive 


76 


THE    PHOTOGRAPHIC    NEGATIVE. 


the  pyroxyline  of  its  solvents,  and  to  precipitate  it  in  a  spongy 
mass.  The  stirring  must  be  continued  until  the  precipitated 
mass  feels  firm  and  hard  to  the  touch.  The  water  is  then 
poured  off,  the  cotton  passed  through  a  cloth  and  dried.  It  is 
then  suitable  for  use  in  making  up  the  following  collodion : 

Alcohol 1  ounce 

Ether 2  ounces 

Double  bromide  of  cadmium  and  ammonium 14  grains 

Zinc  bromide .  .14  grains 

Precipitated  pyroxyline,  common 7  grains 

Precipitated   pyroxyline,    made   by   the   nitrate   of 

potassium  method 28  grains 

A  stock  of  this  can  be  made  up,  as  it  keeps  well.  It  should 
not  be  filtered,  but  should  be  decanted  off  when  wanted. 

The  sensitive  modification,  or  collodio-bromide  emulsion,  is 
produced  by  adding  to  each  ounce  of  the  above  collodion  6.2 
grains  of  finely-powdered  nitrate  of  silver  dissolved  in  3  ounces 
of  alcohol.  To  effect  solution,  the  powdered  nitrate  is  placed 
in  a  flask  with  a  few  drops  of  distilled  water ;  solution  is  pro- 
duced by  gentle  heat ;  the  alcohol  is  then  added  and  the  pre- 
cipitate first  formed  is  re-dissolved  by  heat.  This  solution  is 
added,  drop  by  drop,  to  the  given  quantity  of  collodion.  The 
apparatus  shown  in  Figure  17  will  be  found  very  convenient 
for  this  purpose,  as  well  as  for  others,  when  a  finely  divided 
emulsion  is  required. 

A  and  C  are  two  flasks ;  B  is  a  cork,  through 
which  are  passed  two  glass  tubes  as  shown,  the 
lower  end  of  the  tube  projecting  into  the  bottle, 
C,  having  been  drawn  to  a  point,  and  then  filed 
off,  thus  leaving  a  small  orifice. 

The  collodion  is  placed  in  the  lower  flask,  the 
silver  solution  in  the  upper.    By  vigorous  shaking, 
the  nitrate  solution  is  made  to  pass,  drop  by  drop, 
into  the  collodion,  and  in  this  way  a  very  finely- 
divided  emulsion  is  produced,   which  may  be 
C   tested  by  pouring  a  few  drops  on  a  glass,  and  ex- 
amining it  by  white  light.     If  it  shows  a  bluish 
FIG.  17.         tint  by  reflected  and  an  orange  tint  by  trans- 
mitted light,  the  operation  has  been  successful  thus  far. 


COLLODION    EMULSION.  77 

The  emulsion  is  now  set  aside  in  the  dark  for  thirty-six 
hours,  to  settle  and  ripen. 

The  next  step  is  to  test  for  silver  nitrate,  which  must  be 
slightly  in  excess.  For  this  purpose,  an  ounce  of  distilled 
water  is  placed  in  a  beaker  glass,  and  a  dram  of  the  emulsion 
poured  into  it ;  the  mixture  is  well  shaken,  and  then  filtered 
twice,  or  until  clear,  through  filter-paper.  The  addition  of  a 
few  grains  of  common  salt  to  the  waste  water  will  indicate 
the  presence  of  free  nitrate  by  a  slight  milkiness,  due  to  the 
formation  of  chloride  of  silver.  If  no  change  in  color  is  vis- 
ible, a  sufficient  .quantity  of  the  alcoholic  nitrate  solution  is 
added  to  the  collodion,  to  produce  a  slight  milkiness  in  the 
wash-water. 

In  order  to  secure  immunity  from  fog  it  is  well  to  add  at 
this  stage  to  every  ten  ounces  of  emulsion  two  drams  of  the 
following  cobaltic  collodion : 

Alcohol   1      ounce 

Ether \%  ounces 

Chloride  of  cobalt 60      grains 

Pyroxyline 12      grains 

The  finished  emulsion  is  next  poured  in  a  fine  stream  into  a 
large  quantity  of  water,  with  constant  stirring.  This  precipi- 
tates the  emulsion  and  removes  from  it  most  of  the  useless  or 
harmful  bye-products.  The  precipitate  is  washed  in  many 
changes  of  filtered  water,  and  finally  in  one  change  of  distilled 
water.  It  is  then  drained  in  a  cloth  and  dried  on  several  thick- 
nesses of  blotting  paper.  When  dry  the  resulting  powder  may 
be  preserved  indefinitely  by  placing  in  a  clean  bottle  well 
wrapped  in  non-actinic  paper. 

Be-emulsification. — To  make  the  final  emulsion  for  coating 
the  plates,  17  grains  of  the  sensitive  powder  are  dissolved  in 
the  following  solution  : 

Alcohol %  ounce 

Ether ' Bounce 

Precipitated  quinine 1  grain 

The  precipitated  quinine  is  made  from  common  sulphate  of 
quinine  by  dissolving  it  in  sulphuric  acid  and  precipitating 
with  ammonia. 


78  THE  PHOTOGRAPHIC  NEGATIVE. 

The  precipitate  is  first  added  to  the  alcohol,  then  filtered  and 
the  ether  added,  and  lastly  the  sensitive  powder.  The  mixture 
is  allowed  to  stand  for  some  hours  in  the  dark,  being  occasion- 
ally shaken ;  it  is  then  filtered  through  cotton  wool  and  used 
to  coat  the  plates. 

Develop  with  any  of  the  usual  developers. 

These  plates  keep  well,  but  are  not  more  than  one-half  as 
quick  as  ordinary  wet  plates. 

Cooper's  Process. 

THE  PLAIN  COLLODION. 

Alcohol 6  ounces 

Ether 10  ounces 

Pyroxyline,  ordinary 160  grains 

THE  EMULSION. 

a.  Alcohol 5  ounces 

Bromide  of  zinc  400  grains 

b.  Alcohol 3  ounces 

Nitrate  of  silver 150  grains 

Dissolve  as  recommended  above. 

To  make  about  ten  ounces  of  emulsion  add  one  ounce  of  a, 
and  all  of  i,  to  three  ounces  of  the  plain  collodion ;  then  add 
twenty  drops  of  syrupy  lactate  of  ammonia.  The  silver  solu- 
tion should  be  at  the  boiling  point  when  added  to  the  collo- 
dion. The  zinc  solution  will  throw  down  a  deposit  after  being 
kept,  which  must  not  be  disturbed. 

The  emulsion  will  ripen  in  twenty-four  hours,  but  better 
results  are  obtained  by  allowing  it  to  stand  for  three  days ;  then 
add  twenty  drops  of  strong  nitric  acid  and  shake  well. 

Wash  first  in  a  very  dilute  solution  of  nitric  acid,  one-half 
an  ounce  of  acid  to  one  gallon  of  water,  then  in  many  changes 
of  pure  water,  and  dry  thoroughly. 

When  dry  dissolve  the  pellicle  in  five  ounces  of  alcohol  and 
the  same  quantity  of  ether. 

The  plates  are  first  coated  with  the  following  gelatine  sul> 
stratum : 

Gelatine 60  grains 

Water 8  ounces 

Chrome  alum  (10  grain  solution) 2  drams 

The  gelatine  is  swelled  in  cold   water,  well  drained,  and 


COLLODION    EMULSION.  79 

• 

enough  boiling  water  added  to  make  the  bulk  up  to  eight 
ounces.  Then  the  alum  solution  is  adde.d  and  the  mixture  well 
stirred  for  a  few  moments,  and  then  filtered,  avoiding  air 
bubbles.  This  solution  is  flowed  over  the  washed  plates  while 
still  wet.  Two  coats  are  given,  the  first  being  drained  away 
closely.  The  plates  are  then  dried  in  an  airy  place,  free  from 
dust. 

The  plates  are  coated  with  the  emulsion,  and  when  the  films 
are  set  they  are  to  be  well  washed ;  a  grooved  negative  washing- 
box  answers  well  for  this  purpose.  Wash  until  all  signs  of 
greasiness  have  disappeared,  and  then  immerse  for  one  minute 
in  the  following  bath  : 

Albumen,  dried 60  grains 

Water 3  ounces 

Ammonia 1  dram 

Again  wash  well,  flow  over  with  a  two-grain  gallic  acid  pre- 
servative, drain  and  dry. 

These  plates  seem  to  possess  indefinite  keeping  qualities, 
develop  well  with  any  good  alkaline  developer,  and  possess 
great  latitude  of  exposure.  They  should  be  backed  to  prevent 
halation.  A  good  backing  is  made  as  follows  : 

Powdered  burnt  sienna  . .    1  ounce 

Gum 1  ounce 

Glycerine 2  drams 

Water 10  ounces 

This  is  applied  to  the  back  of  the  plate  with  a  stiff  brush, 
and  washed  off  with  a  damp  sponge  previous  to  development. 

Capt.  Abney's  Collodio-A  Ibumen  Emulsion. 
PLAIN  COLLODION. 

a.  Alcohol 4  drams 

Ether 6  drams 

Pyroxyline 16  grains 

BROMIDE  SOLUTION. 

b.  Bromide  of  zinc 16  grains 

Chloride  of  calcium 4  grains 

Alcohol 1  dram 

Add  bromine  water  to  impart  a  yellow  tint. 

ALBUMEN  SOLUTION  FOR  EACH  HALF  OUNCE  OF  COLLODION. 

c.  White  of  egg 8  drops 

Alcohol...  1  dram 


80  THE    PHOTOGKAPHIC    NEGATIVE. 

• 

Add  the  albumen  in  drops  and  stir  well. 

First  add  b  to  #,  and  then  drop  in  the  proper  quantity  of  c, 
and  stir  well.  Then  by  the  method  given  on  page  76  add 
forty  grains  of  nitrate  of  silver,  previously  dissolved  in  the 
smallest  quantity  possible  of  water  and  hot  alcohol. 

The  emulsion  is  then  poured  out  into  a  shallow  dish  to  set ; 
it  is  then  washed  as  usual.  Capt.  Abney  recommends  covering 
it  with  a  weak  solution  of  nitrate  of  silver  after  the  second 
washing,  and  then  to  continue  the  washing  until  the  traces  of 
silver  are  very  faint. 

The  pellicle  should  be  re-dissolved  in  equal  quantities  of 
ether  and  alcohol,  in  the  proportion  of  seven  grains  of  the 
pellicle  to  each  ounce  of  the  mixed  solvents. 

After  being  coated,  the  plates  are  well  washed,  flooded  with 
a  two-grain  gallic  acid  preservative,  and  dried. 

These  plates  are  more  rapid  than  ordinary  wet-plates,  and 
can  be  developed  with  any  of  the  alkaline  or  ferrous  oxalate 
developers. 

Capt.  Abney's  Collodio- Chloride  Emulsion,  with  Excess  of 
Chloride. 

This  emulsion  can  be  used  within  a  quarter  of  an  hour  of  its 
preparation.  The  process  is  described  in  Captain  Abney's  own 
words. 

Weigh  out  the  following : 

Pyroxyline,  easily  soluble 10  grains 

Pyroxyline,  easily  soluble 5  grains 

Chloride  of  calcium 20  grains 

Nitrate  of  silver 50  grains 

Dissolve  the  calcium  in  one-half  ounce  of  alcohol,  by  warm- 
ing over  a  spirit-lamp.  Place  the  five  grains-of  pyroxyline  in  a 
two-ounce  bottle,  and  pour  on  it  the  alcohol  containing  the  cal- 
cium. After  a  couple  of  minutes,  add  one-half  ounce  of  ether, 
when  the  cotton  will  dissolve. 

Dissolve  the  50  grains  of  silver  in  a  test  tube  in  25  drops  of 
water,  and  add  to  it  one  ounce  of  boiling  alcohol  and  'mix. 
Previous  to  this,  the  10  grains  of  pyroxyline  should  have  been 
placed  in  a  four-ounce  bottle,  and  the  alcohol  containing  the  silver 
should  be  poured  in.  Next  add  one  ounce  of  ether,  little  by 


COLLODION    EMULSION.  81 

little,  with  continuous  shaking.  Take  the  two  bottles  into  a 
room  lighted  by  yellow  light,  and  gradually  pour  the  chloride 
of  calcium  collodion  into  the  nitrate  of  silver  collodion.  A 
test  plate  should  now  be  coated,  washed  under  the  tap,  and 
placed  in  the  dark  slide.  The  slide  should  be  taken  into 
white  light  and  half  the  front  pulled  up  for  a  second  and  then 
closed.  The  ferrous  citro-oxalate  developer  given  below  should 
then  be  applied  and  the  result  noted.  The  film  should  show  no 
blackening  except  on  the  exposed  half  of  the  plate.  Should 
blackening  take  place,  add  two  or  three  drops  of  a  20-grain 
solution  of  chloride  of  gold  or  cobalt  to  the  emulsion  and 
shake  well ;  the  fog  will  then  disappear. 

There  seems  to  be  no  advantage  in  washing  the  emulsion. 
The  coated  plates  are  washed  and  then  flooded  once  with 

Beer 5  ounces 

White  sugar , 1  lump 

Pyrogallic  acid 5  grains 

Or  the  two-grain  gallic  acid  preserver  may  be  substituted. 
These  plates  will  be  fonnd  quite  sensitive. 

They  are  developed  with  the  ferrous  citro-oxalate  developer, 
prepared  as  follows : 

Citrate  of  potassium,  neutral 100  grains 

Ferrous  oxalate 22  grains 

Water 1  ounce 

First  dissolve  the  citrate  by  heat,  and,  when  nearly  boiling, 
add  the  ferrous  oxalate  and  shake  well. 
A  weaker  form  of  the  same  developer  is 

Citrate  of  potassium 50  grains 

Ferrous  oxalate 12  grains 

Water 1  ounce 

These  solutions  keep  well  when  corked  in  bottles. 

The  plates  are  first  rinsed  in  water,  and  then  immersed  in 
the  developer.  The  image  soon  appears,  and  is  of  an  ivory- 
black  tone,  well  adapted  to  collodion  transfers  or  positives  on 
glass  or  paper.  If  a  warmer  tint  is  desired,  tone  with 

Nitrate  of, uranium 10  grains 

Ferricyanide  of  potassium 10  grains 

Water  .  .  10  ounces 


82  THE    PHOTOGEAPHIC    NEGATIVE. 

Canon  BeecTiey's  Process. 

This  is  a  very  simple  and  reliable  process.  Plates  made  by 
it  possess  admirable  keeping  and  technical  qualities  of  about 
one-half  the  sensitiveness  of  average  wet-plates. 

The  following  solutions  are  made  up : 

1. — BKOMIZED  STOCK  SOLUTION. 

Bromide  of  cadmium  (anhydrous) 300  grains 

Alcohol  (805) ' 8  ounces 

The  solution  is  allowed  to  settle  until  clear.  The  super- 
natant liquid  is  then  carefully  decanted  off,  and  one  dram  of 
hydrochloric  acid  is  added.  In  this  condition  the  solution  will 
keep  for  years. 

2. — COLLODION. 

Bromized  solution   Bounce 

Absolute  ether 9  drams 

Pyroxyline 12  grains 

These  ingredients  are  placed  in  a  clean  bottle  and  shaken 
until  the  pyroxyline  is  dissolved.  The  quantity  given  above 
is  sufficient  to  coat  one  dozen  whole  plates. 

3. — THE  SENSITIZER. 

Nitrate  of  silver 40  grains 

Alcohol v. 1  ounce 

The  best  way  of  effecting  solution  is  to  pulverize  the  silver 
in  a  mortar.  The  powder  is  then  placed  in  a  test  tube,  the 
alcohol  poured  over  it,  and  boiled  until  solution  is  effected. 
It  is  then  poured  in  a  fine  stream  into  the  collodion,  with  con- 
stant stirring.  The  emulsion  is  allowed  to  stand  for  twenty- 
four  hours  in  a  dark  place,  being  occasionally  shaken.  It  is 
then  ripe  enough  for  use,  and  should  have  a  creamy  appearance. 

The  plates  to  be  coated  must  first  have  been  given  a  sub- 
stratum. Any  of  those  given  in  Chapter  IY.  will  answer. 
They  are  then  coated  as  usual,  and,  when  set,  washed  in  pure 
water  until  all  greasiness  has  disappeared.  They  are  then  im- 
mersed in  the  preservative — stale  beer  thirty  ounces,  pyro 
thirty  grains — and  dried  as  usual. 

Before  coating,  the  emulsion  should  be  well  shaken  and 
filtered. 


COLLODION    EMULSION.  83 

Development — Any  good  alkaline  developer  will  work  well 
with  these  plates.  Before  development  the  plates  must  be 
immersed  in  pure  water  to  remove  the  preservative. 

DEVELOPERS  FOK  COLLODION  EMULSION  PLATES. 

Alkaline  Developers. 

l. 

a.  Pyrogallic  acid 6  grains 

Water ...    1  ounce 

b.  Bromide  of  potassium 20  grains 

Water 1  ounce 

c.  Ammonia 1  ounce 

Water 32  ounces 

To  develop :  Take  two  parts  of  a,  two  parts  of  J,  and  one 
part  of  c. 

2. 

a.  Pyrogallic  acid 6  grains 

Alcohol 1  ounce 

b.  Bromide  of  potassium 120  grains 

Water 1  ounce 

c.  Carbonate  of  ammonium 80  grains 

Water 1  ounce 

Six  drops  of  «,  three  drops  of  5,  and  three  drams  of  c, 
form  the  developer. 

3. 

a.  Carbonate  of  ammonium  (pure) 10  grains 

Bromide  of  potassium 2  grains 

Water 1  ounce 

b.  Pyrogallic  acid 50  grains 

Alcohol 1  ounce 

One  ounce  of  «,  and  fifteen  drops  of  b,  form  the  developer. 
Ferrous-Oxcilate  Developer. 

a.  Ferrous  sulphate 160  grains 

Water *. 1  ounce 

b.  Oxalate  of  potassium  (neutral) 1  ounce 

Water 3  ounces 

Add  one  part  of  a  to  two  parts  of  b  immediately  before 
wanted  for  use. 


84  THE    PHOTOGRAPHIC   NEGATIVE. 

Hydrochinone  Developer. 

a.  Hydrochinone.    .    . 12  grains 

Sulphite  of  soda 60  grains 

Water 1  ounce 

b.  Carbonate  of  soda 60  grains 

Water 1  ounce 

For  the  developer  take  two  ounces  of  a,  one  ounce  of  b, 
and  one  ounce  of  water. 

This  developer,  although  expensive,  is  recommended  by  the 
author  for  fine  work,  especially  for  positives  on  glass  or  paper, 
on  account  of  the  velvety  blackness  of  tone  and  the  clearness 
of  shadows  obtained  by  it.  The  hydrochinone  solution  will 
keep  indefinitely;  the  mixed  developer  can  be  used  to  develop 
many  plates,  and  the  developer  does  not  stain. 

Previous  to  development,  the  plates  should  be  soaked  in 
water  or  alcohol,  as  required,  to  remove  the  preservative. 
Gum  or  albumen  preservatives  dissolve  only  in  alcohol. 
When  the  latter  solvent  is  used,  the  plate  must  be  washed  in 
pure  water  until  all  repellent  action  has  ceased.  The  devel- 
oper is  then  poured  over  the  plate.  If  the  image  is  Slow  in 
appearing,  pour  off  the  developer  and  apply  a  new  one  con- 
taining less  bromide,  or  add  more  of  the  alkaline  solution. 

Intensify,  if  necessary,  with  the  following : 

a.  Pyrogallic  acid 2  grains 

Citric  acid .2  grains 

Water 1  ounce 

b.  Nitrate  of  silver 20  grains 

Water 1  ounce 

Wash  the  plate  well,  and  cover  with  a.  Drop  four  or  five 
drops  of  b  into  the  graduate  and  pour  the  solution  on  the 
plate  into  it ;  then  return  the  mixture  to  the  plate  and  allow 
it  to  act  until  sufficient  density  is  reached. 

Defects. — Those  most  commonly  met  with  in  collodion 
emulsion  plates  are  the  following  : 

Black  spots :  due  to  dust  settling  on  the  film  while  drying. 

Crape  markings :  due,  a,  to  the  solvents  of  the  emulsion 
being  too  aqueous ;  5,  to  failure  to  shake  the  emulsion  before 


COLLODION   EMULSION. 


85 


using  it;  or,  c,  to  the  bromide  of  silver  being  too  coarse, 
owing  to  improper  enralsification. 

Difficulty  in  flowing  the  emulsion  :  due  to  a  deficiency  in 
the  solvents. 

The  films  leave  the  plates :  the  pyroxyline  was  too  tough ; 
use  a  more  powdery  kind. 


CHAPTER  IX. 

THE    GELATINE   PROCESS. 

Gelatine  as  a  vehicle  for  the  suspension  of  the  sensitive  salts 
of  silver  was  recommended  by  Poitevin  as  early  as  1850,  but 
owing  to  the  difficulty  of  obtaining  it  in  the  high  state  of 
purity  necessary  for  photographic  purposes,  and  the  supposed 
greater  facility  and  rapidity  of  manipulation  possessed  by  col- 
lodion, Poitevin's  suggestion  found  but  little  favor. 

Maddox,  King,  Burgess,  and  Kenneth,  during  the  years  1871 
to  1874,  published  formulae  in  which  gelatine  replaced  collo- 
dion as  the  vehicle  of  suspension,  but  it  was  not  till  Bennett,  in 
1878,  discovered  the  extreme  sensitiveness  conferred  upon  a 
gelatino-bromide  emulsion,  by  digesting  it  at  a  high  tempera- 
ture, that  the  new  process  met  with  favor  among  photograph- 
ers. From  that  time  its  advance  has  been  rapid  and  continu- 
ous. Although  the  writer  believes  that  it  is  a  mistake  to  bring 
all  photographic  processes  under  the  rule  of  the  new  claimant, 
he  recognizes  the  immense  advantages  possessed  by  the  gela- 
tine method,  advantages  which  may  well  outweigh  any  defects 
inherent  in  it. 

It  has  been  the  custom  to  give  the  highest  praise  to  the 
modern  process  on  account  of  the  extreme  sensitiveness  easily 
given  to  it.  The  writer,  however,  believes  that  its  best  claim 
for  recognition  is  found  rather  on  the  artistic  side. 

In  the  old  collodion  days  the  operator  having  to  prepare  hi& 
plates  himself  as  he  had  occasion  to  use  them  was  under  the 
temptation  of  unduly  magnifying  the  chemical  aspect  of  hi& 
work  and  to  neglect  somewhat  the  artistic. 

But  the  advent  of  gelatine  dry-plates  has  relieved  the  pho- 
tographer from  the  task  of  preparing  his  plates,  and  left  him 
free  to  devote  all  his  care  and  thought  to  the  production  of 
artistic  results.  Art  is  ever  averse  to  manipulation,  and  now 
that  the  photographer  is  to  a  great  degree  emancipated  from 
the  manipulatory  miseries  inseparable  from  the  collodion  pro- 


THE  GELATINE  PROCESS.  87 

cess,  he  has  the  opportunity  of  becoming  more  of  an  artist — of 
putting  more  of  himself  into  his  work. 

Without  touching  upon  the  many  other  advantages  possessed 
by  gelatino-bromide  plates,  the  author  now  addresses  himself 
to  the  pleasant  task  of  explaining  the  details  of  the  production 
of  the  plates  and  the  development  of  the  image. 

PREPARATION  OF  GELATINE  EMULSIONS. 
General  Observations. 

Theory  of  the  Method. — The  preparation  of  the  gelatino- 
bromide  of  silver  consists  essentially  in  forming  a  precipitate 
of  bromide  of  silver  in  a  warm  solution  of  gelatine  ;  this  pre- 
cipitate must  be  sufficiently  fine  to  remain  in  suspension  in 
the  liquid  in  which  it  is  produced ;  it  is  then  said  to  be  in  a 
state  of  emulsion. 

The  sensitive  bromide  of  silver  is  obtained  by  double  de- 
composition, that  is,  by  combining  a  soluble  bromide  with  ni- 
trate of  silver;  the  result  of  this  combination  is  the  formation 
of  insoluble  bromide  of  silver  and  an  alkaline  nitrate  corres- 
ponding to  the  bromide  employed.  This  nitrate  must  be  re- 
moved by  washing. 

It  is  necessary  that  the  bromide  be  in  excess  in  order  to  pre- 
vent fog  and  to  regulate  the  action  of  the  developing  reagents. 
As  a  result  of  this  there  always  remains  in  the  emulsion  a  cer- 
tain quantity  of  undecomposed  alkaline  bromide,  whic-h,  unless 
removed  by  washing,  would  greatly  lower  the  sensitiveness  of 
the  finished  emulsion. 

The  most  common  mode  of  washing  is  to  allow  the  emulsion 
to  set,  then  to  break  it  up  into  small  pieces  and  to  wash  for 
some  hours  in  many  changes  of  distilled  or  filtered  rain  water. 
During  the  washing  the  emulsion  gradually  gains  in  sensitive- 
ness, owing  to  the  more  complete  removal  of  the  alkaline  ni- 
trate and  bromide.  Hence  the  greatest  precautions  should  be 
taken  against  exposing  the  emulsion  to  the  action  of  any  light 
save  when  absolutely  necessary,  and  then  only  for  the  shortest 
possible  time.  After  the  washing  is  completed,  the  emulsion 
is  freed  from  all  excess  of  water  by  draining,  then  melted  with 
gentle  heat,  filtered,  and  flowed  over  the  plates,  which,  after 
the  film  is  set,  are  dried  and  stowed  away  for  future  use. 


88  THE    PHOTOGKA.PHIC    NEGATIVE. 

Time,  temperature,  and  degree  of  alkalinity  affect  the  sensi- 
tiveness of  gelatino-bromide  emulsions. 

At  low  temperature  great  sensitiveness  is  reached  only  after 
long  digestion.  If  the  temperature  is  raised  to  100  deg.  F.  the 
same  grade  of  sensitiveness  is  reached  after  five  or  six  days.  A 
temperature  of  145  deg.  F.  will  give  the1  same  result  within  three 
or  four  hours.  If  the  emulsion  be  kept  at  the  boiling  point, 
thirty  minutes  gives  the  maximum  of  sensitiveness.  These 
conditions  are  changed  if  any  addition  is  made  with  a  view  to 
produce  a  chemical  ripening.  Ammonia  is  often  employed  for 
this  purpose.  This  produces  an  alkaline  condition  in  the 
emulsion  which  thus  reaches  its  maximum  of  sensitiveness  after 
standing  for  some  hours  in  a  cool  place.  With  this  method  it  is 
not  advisable  to  seek  to  hasten  the  ripening  by  employing  heat. 

Choice  of  Soluble  Bromides. — The  bromides  of  ammonium 
and  potassium  are  the  ones  most  commonly  employed  in  the  man- 
ufacture of  gelatine  emulsions.  There  is  little  choice  between 
them.  Emulsions  prepared  with  one  show  little  or  no  differ- 
ence from  those  prepared  with  the  other.  On  this  point  Eder 
says  that  potassium  bromide,  owing  to  its  stability,  appears 
more  suitable  than  the  hygroscopic  ammonium  salt,  which  dis- 
colors under  the  action  of  light.  Some  operators  use  a  mixture 
of  the  two  salts,  claiming  superior  results,  a  claim  which 
numerous  experiments  of  my  own  have  failed  to  substantiate. 
Either  of  the  two  salts  may  be  employed  without  necessarily 
prejudicing  the  quality  of  the  resulting  emulsion. 

In  substituting  one  salt  for  the  other  it  must  be  remembered 
that  their  combining  weights  are  different,  as  shown  in  the  fol- 
lowing table ;  the  combining  weight  of  the  potassium  bromide  is 
1 1 9,  that  of  the  ammonium  is  98  ;  hence  one  part  of  the  former 
may  replace  0*823  of  the  latter,  or  one  part  of  the  ammonium 
bromide  may  be  replaced  by  1'214  of  the  potassium  salt. 

The  principal  bromides,  chlorides,  and  iodides  which  are 
likely  to  be  used  in  emulsions  of  either  gelatine  or  collodion 
have  been  included  in  these  tables.  Table  No.  I.  presents  to 
the  reader,  without  any  mystification  which  may  be  involved  in 
equivalents,  the  actual  weights  of  haloid  or  silver,  as  the  case 
may  be,  required  to  convert  or  combine  with  one  grain  of  the 
other. 


THE    GELATINE    PROCESS. 


TABLES  FOR  THE  SIMPLIFICATION  OF  EMULSION  CALCULATIONS. 
No   I. 


i  c  -D 

^g 

2*0 

•o  *> 

T3   C 

e/3 

•"  0*3 

0    § 

2.  c 

,2  o'-o 

11 

Js 

"c3  «j 

C-cj  •;••* 

^     '3 

CO    tJD 

tj 

O  "43 

•C   S     i 

•"^  fe'O 

-C   fj  t  —  • 

*    0 

*3 

JJ  >O 

1  sl 

lit 

*••  c 

<L> 

VM          "O 

0  2  M 

pf 

5|i 

**M    °     ^ 

•s^ 

*D 

t^      o 

_r2    ^    hr 

^  o  ^ 

•^     QJ     gj 

43    ^ 

8 

bpo>  c 

D-g'g 

^crbo 

|! 

'51 

^    0. 

||1 

•s| 

l!_ 

Ammonium  bromide  

98 

1-734 

•576 

1-918 

•521 

] 

Potassium  bromide   

119*1 

1-437 

*700 

1-578 

•633 

Sodium  bromide   

103 

1-650 

•606 

1-825 

•548 

Cadmium  bromide,  com  

172 

•988 

1-012 

1-093 

•915 

{1-106 

Cadmium  bromide,  anh  

136 

1-25 

•800 

1-382 

•723 

Zinc  bromide           .  .            . 

112-1 

1-509 

•663 

1-670 

•600 

Ammonium  chloride         ..... 

53-5 

3*177 

•315 

2-682 

•373 

Sodium  chloride 

58.5 

2-906 

•344 

2-453 

•408 

^ 

•844 

Ammonium  iodide 

145 

1-172 

•853 

1-620 

•617 

Potassium  iodide     .          . 

166-1 

1-023 

•977 

1-415 

'707 

1 

Sodium  iodide 

150 

1-133 

•882 

1-566 

•638 

L  1-383 

Cadmium  iodide            .           .  . 

183 

•929 

1-076 

1-284 

•778 

J 

In  order  to  test  the  utility  of  this  table,  let  us  suppose  that 
it  is  desired  to  make  (say)  ten  ounces  of  emulsion  by  a  new 
formula,  which,  for  the  saKe  of  showing  the  working  of  the 
table,  we  write  down  as  follows  : 

Bromide  of  potassium 150  grains 

Iodide  of  Potassium 10  grains 

Chloride  of  ammonium 10  grains 

Gelatine 200  grauis 

Now  we  want  to  know  how  much  silver  nitrate  should  be 
employed  in  sensitizing  this  mixture.  For  this  purpose  we 
use  the  first  column,  in  which  we  find  against  each  haloid  the 
exact  quantity  of  silver  nitrate  required  to  fully  decompose  one 
grain.  Taking,  then,  the  figures  we  find  in  column  No.  1 
against  the  three  salts  in  the  above  formula,  and  multiplying 
them  by  the  number  of  grains  of  each  used,  we  have  the  fol- 
lowing sum : 


Potassium  bromide 150  X  1'427  =  214 

Potassium  iodide 10  X  1*023  =    10'23 

Chloride  of  ammonium. ..  10  X  3*177  =    31*77 


Weight 

silver  nitrate 

required. 


or  the  total  quantity  of  silver  nitrate  required  for  full  conver- 
sion, 256*00  grains. 


90 


THE    PHOTOGRAPHIC    NEGATIVE. 


Cadmium 
Iodide. 

10 

? 

§ 

CO 

§ 

? 

5 
t- 

•B 

i 

05 
CO 

§ 
i> 

i 

OS 
00 

v* 

Sodium. 
Iodide. 

1 

1 

i 

(O 

I 

to 
t- 

s 

CO 

C5 
CO 

1 

1 

1-1 

P 

Potassium 
Iodide. 

OS 

t- 
t- 

p 

! 

~ 

S 

i 

1 

I 

co 

£ 

i-i 

i 

1 

Ammonium 
Iodide. 

«o 

1 

£ 

l 

QO 

P 

s 

1 

co 

> 

r^ 

i« 

-«j< 

1 

! 

Sodium 
Chloride. 

1O 

1 
<N 

§ 

^ 
« 

<N 

! 

•* 

cs 

- 

1 

jq 

e§ 

00 
O} 

i 

CJ 

§ 

CO 

Ammonium 

§ 

1 

§ 

i- 
?» 

§ 

3 

1H 

§ 

01 

r^ 

s 

§ 

oo 

o» 

•^ 

1-H 

<M 

1-H 

e«3 

0> 

<M 

TH 

e« 

CO 

20 

co 

•      Zinc 
Bromide. 

t~ 

9> 

! 

>O 

5s 

! 

! 

<H 

1^1 
t- 

Oi 

o 

S5 

C4 

1 

Ci 

§§ 

T^H 

! 

Cadmium 
Bromide. 
(Anhyd.) 

o} 
t- 

I 

g 

§ 

o* 

rH 

g 

00 

I 

cc 
T1 

! 

§1 

CO 

o 

»o 

i 

Cadmium 
Bromide. 
(Coml.) 

» 

I 

I 

<-< 

? 

i 

5o 

s 

CO 
QO 

1 

« 

QO 

! 

Sodium 
Bromide. 

1 

i 

<H 

6 

P 

CO 

8 

OS 

oo 

<g 

•3D 

i 

OJ 

s 

! 

g 

Potassium 
Bromide. 

i 

*4 

I 

1 

^T 

i- 

os 

? 

t- 

?« 

! 

s 
« 

! 

Ammonium 
Bromide. 

^H 

1O 

« 

S 

o 

p 

i 

OS 

CO 

•  *p 

i 

1 

o 

o 

« 

c- 

s 

* 

B 

§ 

0 

x: 
e 
cfl 

6 

Ammonium  bromi 

Potassium  bromid 

Sodium  bromide  . 

Cadmium  bromide 

Cadmium  bromide 

Zinc  bromide  

Ammonium  chlori 

Sodium  chloride.. 

Ammonium  iodid< 

T3 

-5 
o 

E 

3 

rt 

O 

CU 

Sodium  iodide.  .  . 

Cadmium  iodide. 

THE    GELATINE    PROCESS.  91 

Table  No.  II.  gives  in  separate  columns  the  relative  convert- 
ing values  of  each  of  the  soluble  haloid  salts  in  ordinary  use, 
showing  how  much  of  any  salt  must  be  used  to  replace  one 
grain  of  any  other.  In  each  column  will  be  found  an  unit 
(printed  in  larger  type)  which  represents  one  grain  of  the  salt 
named  at  the  head  of  the  column  ;  the  other  figures  in  the 
same  column  show  the  exact  quantities  of  the  other  salts  which 
must  be  used  in  lieu  of  a  single  grain  of  that  particular  haloid. 
Thus,  taking  the  first  column,  which  is  headed  "  Ammonium 
Bromide,"  we  find  against  ammonium  bromide  in  the  margin 
the  figure  1,  representing  one  grain  of  that  salt.  If  we  wish  to 
know  the  relative  converting  power  of  potassium  bromide  we 
take  the  number  in  the  same  column  which  stands  against  the 
latter  salt  in  the  margin,  viz.,  1/215  ;  that  is  to  say,  1/215  grain 
of  potassium  bromide  will  be  required  to  do  the  same  work  as 
one  of  NH4  Br. 

Choice  and  Treatment  of  the  Gelatine. — The  gelatine  em- 
ployed must  have  been  prepared  especially  for  photographic 
purposes,  and  a  supply  both  of  the  hard  and  the  soft  varieties 
should  be  kept  on  hand.  An  emulsion  prepared  with  a  mix- 
ture of  both  hard  and  soft  gelatines  gives  better  films  than  one 
in  which  either  the  hard  or  the  soft  alone  was  used.  In  win- 
ter, equal  proportions  of  the  two  should  be  used;  in  summer, 
the  proportion  of  the  hard  variety  should  be  increased  to  two- 
thirds  of  the  total  amount  employed. 

The  gelatines  manufactured  by  Cox,  Nelson,  Coignet,  Hein- 
rich  or  Simeon  will  be  found  the  best.  Even  when  the  best 
gelatines  are  employed,  the  operator  will  often  be  troubled  with 
grease  spots  in  his  films;  to  avoid  this  danger  the  author 
recommends  that  the  gelatine  solution  be  purified  in  one  of 
the  following  ways: 

To  each  thirty-five  ounces  of  gelatine  solution  add  the  white  of 
one  egg  beaten  to  a  froth.  Mix  well  and  boil  for  fifteen  minutes 
in  a  water  bath.  The  albumen,  coagulated  by  the  heat,  frees 
the  gelatine  from  all  impurities.  When  cooled  down  to  100 
deg.  the  liquid  is  filtered.  This  method  removes  all  danger 
from  grease  spots,  but  when  the  nitrate  of  silver  is  added  to  a 
gelatine  solution  thus  treated,  a  precipitate  is  formed  which 


92  THE    PHOTOGRAPHIC    NEGATIVE. 

must  be  removed  by  decantation.  Another  equally  good 
method  is  to  soak  the  gelatine,  cut  up  in  shreads,  for  an  hour 
in  a  one  per  cent,  potassium  bromide  solution,  and  then  wash 
in  three  or  four  changes  of  water.  Excess  of  water  is  then 
removed  by  squeezing  the  gelatine  wrapped  in  a  piece  of  clean 
muslin.  The  mass  is  then  weighed,  and  the  difference  in 
weight  between  the  dry  and  the  wet  gelatine  is  deducted  from 
the  amount  of  water  directed  to  be  added  to  form  the  emul- 
sion. It  is  well  to  test  the  gelation  solution  with  litmus  paper. 
If  it  shows  an  acid  reaction,  neutralize  with  ammonia ;  if  alka- 
line, neutralize  with  a  few  drops  of  a  ten  per  cent,  nitric  acid 
solution.  In  this  case  do  not  add  the  acid  indicated  in  the 
formulae. 

Proportion  of  the  Ingredients. — Great  diversity  exists  in 
the  proportions  used  of  the  various  ingredients  used  in  making 
an  emulsion.  The  following  table  gives  an  average  computed 
from  the  comparison  of  many  formulae. 

Water 1  ounce 

Bromide  of  ammonium 15  to  20  grains 

or, 

Bromide  of  potassium 18  to  25  grains 

Nitrate  of  silver,  proportioned   to   the  amount 

of  bromide 25  to  30  grains 

Gelatine 30  to  40  grains 

The  proportion  of  gelatine  varies  according  to  its  nature  and 
the  temperature.  In  summer  more,  in  winter  less. 

The  amount  of  emulsion  required  to  coat  the  plates  is  not 
constant ;  from  four  to  five  drams  for  a  whole  plate  is  about 
right. 

Emulsifying. — To  dissolve  the  gelatine  and  to  make  the 
emulsion,  it  is  best  to  use  a  hot  water-bath,  and  to  place  the 
emulsion  in  a  clean  glass  or  porcelain  flask  capable  of  with- 
standing heat  and  sudden  changes  of  temperature.  For  ex- 
perimental work  on  a  small  scale  very  simple  arrangements 
will  suffice ;  a  tin  pail,  an  old  coffee  pot,  or  any  similar  vessel 
with  a  tightly  fitting  cover,  will  answer  for  the  water  bath,  and 
the  emulsion  may  be  placed  in  a  stout  bottle,  a  porcelain  cap- 
sule, or  a  Bohemian  glass  of  suitable  shape  and  size.  But  for 


THE    GELATINE    PROCESS. 


93 


more  ambitious  attempts  something  more  elaborate  must  be 
devised.  The  writer  knows  of  nothing  better  than  one  of  the 
two  arrangements  figured  and  described  below.  The  first, 
shown  in  Fig.  18,  is  a  somewhat  elaborate  emulsifying  apparatus 
recommended  by  David  and  Scolik,  and  is  well  adapted  for 
work  on  a  large  scale. 

Fig.  19  shows  the  apparatus  devised  by  M.  Davanne,  and 
it  is  the  best  with  which  the  writer  has  experimented,  as  it 
combines  in  itself  all  the  requirements  of  emulsifying,  filtering 
and  washing. 


FIG.  18. 

The  essential  parts  of  this  apparatus  consist  of  the  lamp,  F, 
the  sheet-iron  covering,  A,  and  the  cover,  B.  The  lamp  can  be 
filled  and  the  flame  regulated  from  the  outside  as  shown  in 
the  cut.  D  is  a  small  window  of  ruby  glass  through  which  the 
flame  can  be  seen.  A  is  the  water- bath  in  which  the  vessel 
containing  the  emulsion  is  placed.  It  is  provided  with  a  dou- 
ble bottom.  B  is  the  cover,  closed  at  the  top  with  a  small  bent 
pipe  soldered  in  to  allow  the  steam  to  escape.  This  cover  must 
fit  light-tight  over  A.  This  is  easily  effected  by  soldering  a 
small  gutter-shaped  trough  around  the  top  of  A,  into  which  the 
bottom  of  B  fits.  By  filling  this  trough  with  small  shot  a 
light-tight  joint  is  made. 

The  dimensions  of  the  various  parts  will  depend  upon  the 
quantity  of  emulsion  to  be  cooked.  I  have  had  no  experience 
with  this  apparatus,  but  it  is  theoretically  good,  and  should 


94  THE    PHOTOGRAPHIC   NEGATIVE. 

work  well  if  properly  constructed.  A  very  good  substitute 
for  it  is  found  in  the  infants'  food- warmer,  to  be  had  of  most 
druggists,  which  consists  essentially  of  a  covered  porcelain  jar 
resting  in  a  metallic  water-bath,  the  water  in  which  is  heated 
by  means  of  a  candle  placed  underneath. 

Fig.  19  illustrates  M.  Davanne's  ingenious  apparatus. 


FIG.  19. 


It  is  simply  a  common  steam  cooker  somewhat  modified  to 
adapt  it  to  its  new  use.  A  is  the  hot  water  receptacle ;  B,  fit- 
ting tightly 'over  A,  contains  the  vessel  in  which  the  emulsion 
is  placed  ;  d,  d,  are  two  small  tin  tubes  soldered  into  B,  which 
serve  to  convert  the  apparatus  into  a  convenient  washing  ar- 
rangement. To  construct  the  apparatus  the  perforated  bottom 
is  removed  from  B,  leaving  a  margin  of  one-quarter  of  an  incli 
around  B  to  receive  the  movable  plates  used  in  the  different 
operations.  The  portion  removed  is  used  as  a  false  bottom  in 
A  to  prevent  breakage  of  the  various  flasks  which  may  be  placed 
there.  Its  place  in  B  is  filled  by  a  movable  plate,  F,  pierced 
with  holes.  On  this  plate  all  the  preparations  are  placed  which 
are  to  be  heated  with  steam  instead  of  warm  water. 

Three  or  four  other  metal  plates  are  provided,  of  the  form 
shown  at  E,  with  various  sized  openings.  These  are  intended  to 


THE    GELATINE    PROCESS.  95 

hold  funnels  for  warm  filtration,  or  flasks  containing  solutions, 
the  temperature  of  which  requires  careful  watching. 

The  following  description  will  demonstrate  the  great  adapta- 
bility of  this  simple  piece  of  apparatus : 

Cooking  the  Emulsion. — The  flask  containing  the  emulsion 
is  placed  on  the  false  bottom,  the  cover  is  put  on  and  the  tubes 
d,  d,  closed  with  corks,  and  the  water  brought  to  the  proper 
temperature ;  or  the  flask  is  placed  on  the  perforated  bottom  of 
B,  and  the  emulsion  cooked  by  steam. 

Filtering. — The  filter  is  placed  in  one  of  the  metallic  plates, 
E,  in  such  a  way  that  it  is  nearly  introduced  into  B,  a  flask  is 
placed  beneath  it,  and  the  water  is  heated ;  the  heat  thus  pro- 
duced is  sufficient  to  prevent  the  emulsion  from  closing  the 
pores  of  the  filtering  medium. 

Washing. — The  shredded  emulsion  is  placed  in  a  wide- 
mouthed  flask  fitted  with  a  cork,  through  which  pass  two  glass 
tubes,  one  reaching  nearly  to  the  botton,  the  other  only  a  few 
inches;  the  tubes  d,  d,  are  closed  with  corks  carrying  glass 
tubes  which  are  connected  with  the  tubes  in  the  flask  by  means 
of  black  india-rubber  piping.  The  tube  thus  attached  to  the 
longer  tube  in  the  flask  is  connected  with  the  tap  by  rubber 
piping.  The  writer  confidently  recommends  this  apparatus  to 
all  experimenters  as  a  most  convenient  and  compact  arrange- 
ment. 

Filtration. — All  emulsions  must  be  filtered  before  the  plates 
are  coated.  To  effect  this  in  the  case  of  emulsions  containing 
gum  or  gelatine,  it  is  often  necessary  to  resort  to  the  method  of 
warm  filtration  to  prevent  the  pores  of  the  filtering  medium 
from  being  closed.  Small  quantities  of  emulsion  are  easily 
filtered  through  a  clean  lamp  chimney,  around  the  top  of  which 
two  or  three  thickness  of  clean  linen  have  been  tied.  Another 
good  method,  as  it  avoids  air  bubbles,  is  the  method  of  upward 
filtration  already  described. 

For  large  quantities  of  emulsion,  however,  some  means  of 
keeping  the  emulsion  warm  during  the  process  of  filtration 
must  be  resorted  to.  Figs.  12  and  13  (page  19)  illustrate  two 
very  efficient  arrangements  for  warm  filtration.  There  is 
little  choice  between  them,  both  being  constructed  on  the 


96 


THE    PHOTOGRAPHIC    NEGATIVE. 


same  principle.  To  avoid  air  bubbles,  it  is  well  to  bring  the 
tube  of  the  funnel  in  contact  with  the  side  of  the  vessel  into 
which  the  emulsion  is  to  be  filtered. 

If  Davanne's  apparatus  is  used,  neither  of  these  latter  will 
be  needed. 

Silvering. — In  order  to  produce  the  bromide  of  silver  in  the 
extremely  fine  state  of  division  necessary  to  give  good  resultsr 
it  is  imperative  that  the  nitrate  solution  be  added  slowly  to 
the  emulsion.  A  simple  means  of  effecting  this  is  to  add  the 
silver  in  small  quantities,  and  to  shake  well  after  each  addition. 
Another,  and  perhaps  a  better,  is  to  pour  the  silver  solution  into 
the  emulsion  in  a  fine  stream  with  constant  stirring.  A  good 
stirrer  is  made  by  fastening  a  strip  of  glass  across  the  end  of 
a  glass  rod  with  a  piece  of  clean  twine.  A  rotary  motion  is 
imparted  to  the  rod  by  twirling  it  between  the  thumb  and  fore- 
finger. 

An  ordinary  glass  funnel  is  easily  adapted  for  silvering  pur- 
poses, by  inserting  a  clean  cork  in  the  lower  end  of  the  tube 
and  boring  a  small  hole  through  it. 

A  spray  apparatus  is  also  very  efficient  for  this  purpose. 
Fig.  20  shows  a  form  which  is  easily  constructed. 

Two  thin  glass  tubes  are 
bent  in  the  shapes  shown 
at  A  and  B.  The  tube,  A r 
is  drawn  to  close  the  bore. 
A  flat  file  is  then  used  to 
file  away  the  point,  leaving 
a  very  small  orifice.  The 
two  tubes  are  then  fitted 
into  a  cork  which  is  placed 
in  a  test  tube,  as  shown  in 
the  figure.  The  silver  nit- 
rate is  placed  in  the  test 
tube,  the  cork  inserted,  and  a  fine  spray  of  liquid  is  forced 
out  by  blowing  through  the  tube,  B.  The  handiness  of  the 
apparatus  is  increased  by  adapting  to  B,  with  a  piece  of  rubber 
tubing,  a  rubber  ball  provided  with  a  valve. 

The  silvering  apparatus  shown  in  Fig.  17  is  also  very  efficient. 


FIG.  20. 


THE    GELATINE    PROCESS. 


97 


Digesting  the  Emulsion. — The  vessel  containing  the  emul- 
sion is  placed  in  the  water-bath,  which  is  brought  to  the  re- 
quired temperature.  If  the  emulsion  is  to  be  boiled,  a  bent 
glass  tube  should  be  inserted  in  the  cork  which  closes  the  flask. 
Breaking  Up  and  Washing* — After  digesting  the  proper 
length  of  time,  the  emulsion  is  allowed  to  set,  by  pouring  it  out 
into  a  clean  shallow  tray.  When  well  set  it  is  cut  up  into 
narrow  strips  with  a  clean  ivory  paper  cutter ;  the  strips  are 
then  placed  in  the  center  of  a  square  of  working  canvas,  pre- 
viously soaked  in  a  solution  of  carbonate  of  soda  and  well 
washed,  and  squeezed  out  into  a  deep  dish  full  of  clean 
water.  The  washing  can  be  done  in  a  variety  of  ways.  The 
simplest  is  to  wash  in  many  changes  of  water,  stirring  the 
emulsion  well  after  each  change,  and  allowing  it  to  settle  be- 
fore decanting  the  water.  If  this  method  be  adopted  a  double 
tubed  decantation  flask  will  be  found  very  convenient ;  a 
piece  of  clean  muslin  is  tied  over  the  small  tube  and  the 
emulsion  introduced  through  the  large  one.  It  is  well  ta 
squeeze  the  emulsion  through  the  canvas  once  more  when 
half  washed.  A  half  hour's  washing  in  this  way  will  proba- 
bly eliminate  all  the  soluble  salts. 

Capt.  Abney  has  recommended  the 
following  very  simple  washing  appa- 
ratus, the  use  of  which  makes  it  possi- 
ble to  wash  the  emulsion  in  full  day- 
light. Fig.  21  makes  its  construction 
sufficiently  evident.  A  hole  is  perfor- 
ated in  the  lid  of  a  tin  canister  of 
sufficient  size  to  admit  a  glass  tube,  C. 
This  tube  is  connected  with  the  water- 
tap  by  a  piece  of  well-washed  black 
inclia  rubber  piping.  A  spout,  D,  is 
soldered  to  the  canister.  To  prevent 
the  emulsion  from  being  carried  over 
the  top  of  the  flask,  a  piece  of  muslin 
is  tied  over  its  mouth  around  the  glass  tube. 

The  method  of  converting  Davanne's  cooker  into  a  washing 
apparatus  has  already  been  given. 


98  THE    PHOTOGRAPHIC   NEGATIVE. 

When  the  washing  is  nearly  completed  a  small  quantity  of 
the  wash-water  is  placed  in  a  glass  and  a  few  drops  of  a  neu- 
tral solution  of  nitrate  of  silver  are  poured  in.  If  the  mix- 
ture examined  by  white  light  shows  no  coloration  the  washing 
is  sufficient. 

Draining, — When  the  emulsion  is  sufficiently  washed  it  is 
drained  to  remove  the  excess  of  water.  A  hair-sieve  may  be 
used  for  this  purpose,  or  a  piece  of  linen  or  open-meshed  can- 
vas tied  over  the  top  of  a  large  earthen  vessel.  The  emulsion 
should  be  allowed  to  drain  two  hours.  At  the  end  of  that 
time  it  will  be  well  to  pour  a  few  ounces  of  alcohol  over  the 
mass. 

Re-melting. — The  emulsion  is  re-melted  in  the  water-bath  at 
a  low  temperature ;  during  this  process  the  emulsion  should 
be  stirred  occasionally.  When  dissolved  it  is  ready  for  filter- 
ing. 

FORMULAE  FOR  EMULSIONS. 
Andrei's. — Weigh  out  the  following : 

Bromide  of  ammonium 138  grains 

Nitrate  of  silver , 208  grains 

Gelatine 310  grains 

Dissolve  the  ammonium  salt  in  five  ounces  of  water,  and 
add  138. grains  of  the  gelatine  cut  up  into  shreds.  As  soon  as 
the  gelatine  has  swelled,  dissolve  in  the  water-bath. 

While  this  is  taking  place,  dissolve  the  silver  in  two  and  a 
half  ounces  of  water,  with  gentle  heat.  While  both  solutions 
are  warm,  add  the  silver  solution  to  the  gelatine  by  any  of  the 
methods  indicated  above.  This  and  the  following  operations 
must  be  carried  out  by  ruby  light. 

The  silvered  emulsion  is  to  be  kept  at  the  boiling  point  for 
thirty  minutes,  or  until  a  few  drops  of  it,  spread  on  a  strip  of 
glass,  is  blue  by  transmitted  light.  Allow  it  to  cool  down  to 
about  1 20  deg.  and  then  add  eighty-one  grains  of  shredded 
gelatine  previously  swelled  in  cold  water.  When  the  gelatine 
is  dissolved  add  two  drams  of  a  two  per  cent,  bichromate  of 
potash  solution ;  mix  well,  and  pour  out  into  a  clean  porce- 
lain tray  to  set.  When  set  the  emulsion  is  cut  into  shreds, 


THE    GELATINE    PROCESS.  99 

squeezed  through  canvas,  and  washed.  It  is  then  drained, 
eighty-one  grains  of  swollen  gelatine  added  and  dissolved  by 
gentle  heat,  and  poured  out  as  before  to  set.  When  the 
emulsion  is  set  it  is  covered  with  alcohol  and  allowed  to  ripen 
for  eight  days.  It  is  then  melted,  filtered,  and  spread  over 
the  plates. 

Henderson '«  Ammonia  Method. — 
In 

Distilled  water 8^  ounces 

dissolve 

Bromide  of  ammonium 308  grains 

Gelatine  (previously  swelled)  50  grains 

When  cold  add 

Water 1%  ounces 

Alcohol 1%  ounces 

Strong  ammonia 4      drams 

In 

Distilled  water , 3}^  ounces 

dissolve  by  heat 

Nitrate  of  silver. 462  grains 

and  add  gradually  to  the  first  solution. 

An  emulsion  thus  prepared  lacks  sensitiveness.  This  is 
produced  by  allowing  the  emulsion  to  ripen  for  twenty-four 
hours ;  under  the  alkaline  conditions  present  sensitiveness  is 
conferred  in  this  simple  way.  At  the  end  of  twenty-four 
hours  220  grains  of  swelled  gelatine  are  added  and  dissolved 
by  gentle  heat.  Then  proceed  as  above. 

Eder's  Ammonio-Nitrate  of  Silver  Method. — 
In 

Distilled  water 4  ounces 

dissolve 

Bromide  of  potassium 310  grains 

add 

Gelatine 617  grains 

previously  swelled  in  water. 

In 

Distilled  water 4  ounces 

dissolve 

Nitrate  of  silver 462  grains 


100  THE   PHOTOGRAPHIC   NEGATIVE. 

To  this  solution,  cold,  add  strong  ammonia,  drop  by  drop, 
until  the  precipitate  first  formed  is  re-dissolved. 

Add  this  gradually  to  the  first  solution,  and  place  in  a  water- 
bath  at  a  temperature  of  105  deg.  Kemove  the  source  of  heat 
and  allow  the  emulsion  to  cool  down  gradually  to  about  75  deg., 
then  pour  out  to  set,  and  proceed  as  usual.  For  plates  of  mod- 
erate sensitiveness  the  author  prefers  this  method  to  any  others 
with  which  he  has  experimented. 

Brauris  Method. — 
In 

Distilled  water 4  drams 

dissolve 

Bromide  of  ammonium 964  grains 

add 

Gelatine 92  grains 

previously  swelled  in 

Distilled  water 19  ounces 

dissolve 

Nitrate  of  silver 1,543  grains 

and  add  to  the  first  solution  ;  after  a  few  minutes  add 

Strong  ammonia. 12  drams 

and  stir  well. 

For  plates  of  medium  rapidity  digest  for  six  hours  at  a  tem- 
perature of  95  deg.  When  great  sensitiveness  is  desired  digest 
for  twelve  hours  at  the  same  temperature. 

As  soon  as  the  digestion  is  finished,  turn  the  emulsion  out 
into  a  three-gallon  earthen  jar  containing  half  a  gallon  of  dis- 
tilled water.  Put  on  the  cover  and  allow  it  to  stand  for  four 
days  if  it  was  digested  for  twelve  hours,  and  six  days  if  digested 
six  hours.  By  this  time  all  the  sensitive  bromide  of  silver  will 
have  deposited.  The  water  is  then  decanted  and  1,235  grains 
of  gelatine,  swelled  in  39  ounces  of  water,  are  added  to  the 
bromide,  and  well  stirred.  The  mixture  is  melted  at  a  tem- 
perature of  105  deg.  As  soon  as  the  gelatine  is  dissolved,  the 
emulsion  is  filtered  and  used  for  coating  the  plates. 


THE   GELATINE   PROCESS.  101 

This  method  gives  clean  plates,  which  yield  crisp,  brilliant 
negatives,  of  great  clearness  in  the  shadows. 

Scolitts  Ammonio- Nitrate  of  Silver  Method. — 

In 

Distilled  water 17^  drams 

dissolve 


Bromide  of  ammonium 308  grains 

Bromide  of  potassium 370  grains 


and  add 


Iodide  of  potassium  solution  (1  to  10) 2  to  3  drams 

Hard  gelatine 704  grains  )   .        . 

Soft  gelatine 704  grains  [  m  wmter 

or, 

Hard  gelatine 1,003  grains  }  . 

Soft  gelatine    .400  grains  pn  summer 

Allow  the  gelatine  to  soak  for  half  an  hour  in 

Distilled  water 17%  drams 

dissolve 

Nitrate  of  silver 926  grains 

Add  ammonia,  drop  by  drop,  to  re-dissolve  the  precipitate 
first  formed,  stirring  well. 

Dissolve  the  gelatine  in  the  water-bath  at  a  temperature  of 
150  deg.  Then,  in  the  dark  room,  add  the  silver  solution  in  a 
fine  stream,  with  constant  stirring.  Replace  the  emulsion  in 
the  water-bath  for  half  an  hour,  the  source  of  heat  being  with- 
drawn. At  the  expiration  of  this  time  the  emulsion  is  poured 
out  to  set. 

Scolitfs    Modification    of    Henderson's    Cold    Emulsion 
Method.— 
In 

Distilled  water 38  drams 

dissolve  at  120  deg. 

Soft  gelatine 45  to  60  grains 

add 

Citric  acid 15  grains 

when  dissolved  add 

Carbonate  of  ammonia 108  grains 

Bromide  of  ammonium 694  grains 

Iodide  of  potassium  solution  (1  to  10) 2  drams 


102  THE    PHOTOGRAPHIC    NEGATIVE. 

When  these  salts  are  dissolved  add  a  mixture  of 

Alcohol  .........    ..............................  13      ounces 

Ammonia  .....................................  4%  drams 


In 

Distilled  water  ..................................  9%  ounces 

dissolve 

Nitrate  of  silver  ................................  925  grains 

Add  this  to  the  bromized  solution  as  usual,  cork  the  flask 
tightly  to  prevent  the  escape  of  ammonia  fumes,  and  set  aside 
for  twenty-four  hours  to  ripen.  Then  add  1,000  grains  of  soft, 
and  300  grains  of  hard  gelatine,  and  dissolve  at  a  temperature 
of  95  deg.  Set,  wash,  and  filter  as  usual. 

Davannds  Method.  — 
In 

Distilled  water  .................................  12%  ounces 

swell,  dissolve,  and  filter 

Soft  gelatine  ....................................  925  grains 

In 

Distilled  water  .................................  5%  ounces 

dissolve 

Bromide  of  ammonium  ..........................  262  grains 

add 

Gelatine  solution  .............................  ,-3%  ounces 

In 

Distilled  water  ..................................  o%  ounces 

dissolve  at  85  deg. 

Nitrate  of  silver  ..................................  416  grains 

and  add  to  the  bromized  solution  as  usual. 

This  gives  an  excellent  slow  emulsion,  with  the  addition  [of 
3£  ounces  of  the  gelatine  solution.  To  increase  sensitiveness. 
boil  for  half  an  hour,  and  then  add 

Gelatine  solution  ...............................  3%  ounces 

Bichromate  of  potassium  solution  (2  per  cent.).  .  .  .3      drams 


THE   GELATINE   PROCESS.  103 

Burton's  Precipitation  Method. — 
In 

Distilled  water 1%  ounces 

dissolve 

Bromide  of  ammonium 120  grains 

Iodide  of  ammonium 10  grains 

Add 

Soft  gelatine 30  grains 

swell  and  dissolve  at  95  deg.,  and  add 

Hydrobromic  acid 1  drop 

In 

Distilled  water 1%  ounces 

dissolve 

Nitrate  of  silver 212  grains 

and  add  to  the  bromized  solution  in  a  fine  stream. 

Boil  for  thirty  minutes  ;  cool  down  quickly  to  about  60  deg., 
and  then  pour  the  emulsion  in  a  fine  stream  into  a  clean  dish 
containing  eight  ounces  of  alcohol.  In  a  few  seconds  the  emul- 
sion precipitates ;  it  is  then  washed  by  decantation  in  a  few 
changes  of  water,  after  which  it  is  added  to  the  following 
solution  : 

Soft  gelatine 120  grains 

Hard  gelatine 150  grains 

Distilled  water 12  ounces 

The  mixture  is  well  shaken  to  effect  solution ;  the  emulsion 
is  then  filtered  and  used  for  coating. 

This  method  has  many  points  to  recommend  it.  The  plates 
are  of  the  best  quality,  and  yield  plucky  negatives.  The  bro- 
mide of  silver  precipitate  may  be  prepared,  dried  and  pre- 
served indefinitely,  and  the  tedious  operations  of  prolonged 
washing  and  draining  are  done  away  with,  since  a  few  changes 
of  water  serve  to  eliminate  the  last  traces  of  the  soluble  salts 
from  the  precipitated  bromide. 

Fabre's  Method. — By  this  method  the  sensitive  bromide  of 
silver  is  produced  directly  by  macerating  in  a  mortar  the  proper 
proportions  of  bromide  of  silver  and  sulphate  of  potash.  By 
the  addition  of  a  few  drops  of  distilled  water,  long,  needle-like 


104  THE    PHOTOGRAPHIC    NEGATIVE. 

crystals  are  formed ;  the  addition  of  a  slight  excess  of  water 
destroys  this  combination  and  produces  the  sensitive  modifica- 
tion of  bromide  of  silver,  which  may  then  be  emulsified  with 
gelatine  as  usual. 

This  method  does  away  with  washing,  draining,  and  the  use 
of  alcohol ;  and  some  few  experiments  made  with  emulsions 
so  prepared  indicate  remarkably  fine  qualities  in  the  plates. 
To  form  the  sensitive  salts,  mix  intimately  in  a  mortar  one 
part  of  bromide  of  silver  and  two  and  one-fourth  parts  of  sul- 
phate of  potash ;  then  add  of  distilled  water,  drop  by  drop, 
not  more  than  one-tenth  of  the  weight  of  the  bromide.  The 
first  combination  is  formed  within  five  minutes.  A  slight 
excess  of  water  is  then  added ;  this  destroys  the  former  com- 
bination and  forms  the  sensitive  salt,  which,  after  two  or  three 
washings,  may  be  dried  and  preserved  for  future  use,  or  incor- 
porated immediately  with  a  gelatine  solution.  The  emulsion 
is  made  up  as  follows : 

Distilled  water 3%  ounces 

Sensitive  bromide 77      grains 

Gelatine 45  to  75      grains 

Boil  till  a  trial  film  is  blue  by  reflected  light. 

Some  operators  prefer  to  add  the  nitrate  of  silver  to  the 
bromized  solution  in  large  crystals. 

The  following  formulae  and  explanations  are  given  to  illus- 
trate this  method,  which  gives  results  equal  to  the  best. 

In 

Distilled  water 5  ounces 

dissolve 

Bromide  of  potassium 164  grains 

Iodide  of  potassium. . ....  20  grains 

Add 

Soft  gelatine 80  grains 

Allow  the  gelatine  to  soak  for  fifteen  minutes,  and  then  dis- 
solve at  120  deg. 

In  a  strong  bottle  place 

Nitrate  of  silver 232  grains 

Heat  both  vessels  to  140  deg.,  then  add  the  crystals  of  silver 
to  the  bromized  gelatine  and  shake  vigorously  till  the  silver  is 


THE    GELATINE    PROCESS.  105 

dissolved.     Boil   for  thirty  minutes,  then  cool  down  to  100 
degrees. 
Add 

Hard  gelatine 180  grains 

Soft  gelatine 100  grains 

Water to  cover. 

Soak  fifteen  minutes. 

Stir  well  until  the  gelatine  is  dissolved,  and  add 

Strong  ammonia 1  dram 

and  stir  vigorously.     Pour  out  to  set. 

Burton's  Method  for  a  Very  Slow  Emulsion. — 

In 

Distilled  water 3  ounces 

dissolve 

Bromide  of  potassium   160  grains 

Iodide  of  potassium 10  grains 

Soft  gelatine 40  grains 

Soak  the  gelatine   for  fifteen  minutes   before  dissolving; 
when  dissolved,  add 

Hydrochloric  acid 2  drops 

111 

Distilled  water 3  ounces 

dissolve 

Nitrate  of  silver 200  grains 

Heat  both  solutions  to  120  cleg.,  and  add  the  nitrate  gradu- 
ally to  the  gelatine  with  constant  stirring. 
After  ten  minutes,  pour  the  emulsion  over 

Hard  gelatine 150  grains 

previously  swelled  in  cold  water  and  all  excess  of  water  re- 
moved by  pressing  in  a  cloth.  Heat  until  dissolved,  and  set 
aside  to  set.  Then  break  up,  wash,  and  add 

Hard  gelatine 150  grains 

treated  as  before.     Melt,  and  add 

Alcohol . .   4  drams 

Filter  and  coat. 


106  THE   PHOTOGRAPHIC   NEGATIVE. 

Gelatino- Chloride  Emulsion  for  Slides  and  Transparen- 
cies.— 

In 

.  Distilled  water 7  ounces 

dissolve 

Chloride  of  sodium 108  grains 

Gelatine 310  grains 

In 

Distilled   water 3^  ounces 

dissolve 

Nitrate  of  silver 231  grains 

Heat  both  solutions  to  120  deg.,  and  add  the  nitrate  to  the 
gelatine. 

Pour  out  to  set  at  once. 

Wellington's  Citro-  Chloride  Emulsion  for  Opah. — 

In 

Distilled  water 3  ounces 

dissolve 

Chloride  of  sodium  20  grains 

Bromide  of  potassium 40  grains 

Citric  acid 100  grains 

Soft  gelatine 40  grains 

In 

Distilled  water 3  ounces 

dissolve 

Nitrate  of  silver 100  grains 

Citric  acid 100  grains 

Heat  both  solutions  to  150  deg.,  and  add  the  nitrate  to  the 
gelatine. 
Then  add 

Hard  gelatine  (swelled) 200  grains 

and  stir  until  dissolved.     Then  pour  out  to  set. 

These  plates  are  best  developed  with  the  ferrous  oxalate 
developer,  modified  with  chloride  of  ammonium  and  citric 
acid,  as  described  in  the  chapter  devoted  to  development. 


THE    GELATINE    PROCESS.  107 

Sczekely's  Process  with  Carbonate  of  Silver. — 
The  following  solutions  are  made  up : 
1.— In 

Distilled  water 45  drams 

dissolve 

Nitrate  of  silver 261  grains 

2.— In 

Distilled  water 45  drams 

dissolve 

Bicarbonate  of  soda 154  grains 

3.— In 

Distilled  water 45  drams 

dissolve 

Bromide  of  ammonium 154  grains 

Gelatine 340  grains 

Solution  No.  2  is  boiled,  and  then  added  to  No.  1.  The 
precipitate  of  carbonate  of  silver  thus  formed  is  well  washed 
and  thrown  on  a  filter.  When  the  bulk  of  the  liquid  has  run 
through,  the  wet  precipitate  is  placed  in  a  beaker  and  its 
bulk  made  up,  if  necessary,  to  4:5  drams.  Strong  ammonia  is 
then  added,  until  a  clear  solution  is  obtained. 

This  solution  is  poured  gradually  and  with  constant  stirring 
into  solution  No.  3.  The  bottle  is  rinsed  out  with  5  drams 
of  distilled  water,  which  is  added  to  the  emulsion,  which  is 
then  filtered  into  the  funnel,  from  which  it  runs  in  a  fine 
stream.  The  emulsion  must  be  kept  constantly  stirred. 

Sensitiveness  is  given  to  the  emulsion  by  digesting  it  from 
one  to  two  hours  at  a  temperature  of  100  deg. 

All  of  the  operations  preceding  the  addition  of  the  silver 
solution  to  the  bromized  gelatine  may  be  performed  in  diffused 
white  light. 

The  author  finds  that  this  process  gives  negatives  rich  in 
detail  and  gradation,  and  free  from  fog. 

While  the  above  formulae  are  very  far  from  exhausting  the 
long  list  of  gelatine  emulsion  formulae,  they  are  sufficient  to 
meet  all  the  possible  needs  of  the  photographer,  and  with 
proper  precautions  they  are  all  reliable,  and  have  stood  the 


108  THE   PHOTOGRAPHIC    NEGATIVE. 

test  of  practical  experience.  The  writer's  aim  has  been  to 
give  one  typical  formula  of  each  class,  and  he  has  selected 
those  which  his  own  experience  has  proved  to  be  best  adapted 
to  the  special  class  of  work  for  which  they  were  designed. 

Collodio- Gelatine  Emulsions. — The  great  drawback  to  the 
preparation,  in  small  quantities,  of  gelatino  bromide  plates  by 
amateurs  has  been  the  somewhat  difficult  operation  of  coating, 
and  the  need  of  efficient  drying  arrangements. 

To  obviate  these  difficulties  many  experiments  have  been 
made  to  produce  emulsions  combining  the  rapidity  of  the  or- 
dinary gelatine  emulsion  with  the  ease  of  coating  of  collodion. 
The  aim  of  most  of  these  experiments  has  been  to  combine 
pyroxyline  with  the  gelatine  emulsion.  Under  the  usual  con- 
ditions this  is  impossible,  since  the  solvents  of  pyroxyline  pre- 
cipitate gelatine  from  an  aqueous  solution. 

To  Dr,  H.  W.  Vogel  belongs  the  credit  of  being  the  first 
to  overcome  this  difficulty,  and  to  produce  a  combined  emul- 
sion easy  to  coat  with,  and  of  good  working  qualities. 

His  method  is  to  prepare  a  gelatine  emulsion  as  usual,  and 
after  washing  to  dry  it  by  spreading  it  out  on  clean  blotting- 
paper  where  it  is  allowed  to  dry  spontaneously. 

The  dried  pellicle  is  dissolved  by  heat  in  three  to  ten  times 
its  weight  of  acetic  acid,  the  quantity  of  acid  varying  according 
to  the  kind  of  gelatine  used  in  making  the  emulsion.  Enougli 
alcohol  is  then  added  to  make  it  flow  well  at  a  temperature  of 
90  deg. 

Plates  may  be  coated  with  the  emulsion  in  this  condition, 
but,  in  order  to  give  greater  tenacity,  Dr.  Vogel  recommends 
the  addition  of  an  equal  quantity  of  a  collodion  made  as 
follows : 

Pyroxyline 20  grains 

Glacial  acetic  acid 1  ounce 

Alcohol 1  ounce 

Another  method  recommended  by  Dr.  Vogel  is  to  prepare 
a  collodion  emulsion,  any  of  those  described  in  Chapter  VII. 
will  answer.  This  emulsion  is  washed  and  dried.  Seventy 
grains  of  the  pellicle  are  dissolved  in  three  ounces  of  alcoliol 
and  one  and  three-quarter  ounces  of  acetic  acid.  Twenty 


THE    GELATINE    PROCESS.  109 

grains  of  plain  gelatine  are  dissolved  in  three  and  a  half  drams 
of  acetic  acid  and  added  to  it.  The  emulsion  is  then  ready 
for  coating. 

KosarzewnkV s  Method. 

Alcohol 2  ounces 

Glacial  acetic  acid 2  ounces 

Pyroxyline 18  grains 

One  hundred  and  eighty  grains  of  gelatine  emulsion  are 
added  and  dissolved  by  heat. 

Plates  which  are  to  be  coated  with  any  of  these  emulsions 
must  first  receive  a  very  tenacious  substratum,  the  albumen 
and  silicate  of  soda  substratum  answers  well. 

The  emulsion  is  flowed  over  the  plates  like  collodion, 
the  plates  are  drained,  and  then  rocked  gently  to  prevent  the 
formation  of  ridges. 

These  plates  may  be  developed  by  any  of  the  methods  de- 
scribed in  Chapter  XI. 

The  great  advantage  of  this  form  of  emulsion  is  that  it  may 
be  kept  in  a  bottle  and  used  for  coating  plates  as  wanted. 

Sensitiveness  seems  to  be  a  trifle  diminished,  but  the  plates 
yield  good  results. 


CHAPTER  X. 

COATING  THE  PLATES. 

The  Levelling  Shelf. — Some  means  must  be  provided  in  the 
coating-room  for  keeping  the  plates  perfectly  level  while  setting. 
The  most  common  practice  is  to  use  a  glass,  stone,  or  marble 
slab  of  suitable  size.  This  is  levelled  by  means  of  thin  hard- 
wood wedges,  or  by  levelling  screws  of  the  form  shown  in 
Fig.  22.  The  top  screws-  into  the  base.  By  providing  a 
supply  of  these,  and  a  number  of  plate-glass  slabs,  a  large 
number  of  plates  may  be  placed  to  set  on  these  slabs  levelled 
one  above  the  other,  and  left  to  dry  in  the  coating-room,  which 
must  be  light-tight,  well  ventilated,  and  free  from  dust.  This 
method  does  away  with  drying-boxes,  which  are  apt  to  be 
somewhat  uncertain  and  irregular  in  their  action. 

To  prevent  the  troublesome  sticking  of  the  plates  to  the 
le veiling-shelf,  owing  to  the  spreading  of  the  emulsion  on  the 
back  of  the  plate,  the  writer  has  found  it  useful  to  cover  the 
warmed  and  levelled  slab  with  a  plain  gelatine  solution,  made 
insoluble  by  the  addition  of  chrome  alum,  and  then  to  sprinkle 
line  shot  evenly  over  the  coated  surface. 

The  best  results  are  secured  when  plates  coated  with  an 
emulsion  rich  in  gelatine  are  rapidly  set.  In  warm  weather, 
however,  the  films  set  slowly,  and  to  hasten  the  process  Prof. 
Burton  has  devised  the  cooling  arrangement  shown  in  Fig.  23. 
C  is  a  tin  or  zinc  tank,  somewhat  wider  and  longer  than  the 
levelling  slab,  A.  It  is  fastened  securely  to  the  wall,  and, 
when  plates  are  to  be  coated,  it  is  filled  with  ice.  A  faucet  is 
inserted  into  one  end  to  draw  off  the  water. 

Some  coaters  use  a  small  tripod  on  which  the  plate  to  be 
coated  is  placed.  Fig.  24  shows  a  simple  form  which  can  be 
levelled  by  means  of  the  thumb-screws  as  shown. 

The  writer  has  used  with  success,  instead  of  the  customary 
levelling  slab,  the  arrangement  shown  in  Fig.  25. 


COATING    THE   PLATES.  Ill 

JB  .^ 


112  THE   PHOTOGRAPHIC    NEGATIVE. 

The  purpose  of  this  apparatus  is  to  hold  the  plates  firmly 
clamped  end  to  end,  and  in  connection  with  the  coating-box, 
next  to  be  described,  to  allow  the  plates  to  be  rapidly  and  evenly 
coated  without  any  of  the  emulsion  running  over  the  edges, 
as  well  as  to  avoid  the  necessity  of  disturbing  the  plates  until 
the  films  are  well  set. 

To  construct  the  apparatus  a  hard-wood  slab,  of  suitable 
length  and  width,  and  one  inch  thick,  is  smoothly  and  evenly 
planed,  both  surfaces  being  left  perfectly  plane  and  parallel. 
On  the  accuracy  with  which  this  is  done  depends  the  efficiency 
of  the  arrangement.  Along  one  side  a  hard-wood  strip,  B,  one 
and  a  quarter  inches  wide  and  a  half -inch  thick  is  firmly  screwed. 
At  one  end  a  quarter-inch  strip,  half -inch  wide  is  fastened. 
Two  long  strips,  A  A,  of  the  same  thickness,  but  two  inches 
wide,  and  two  short  strips  of  equal  width  and  thickness  are 
next  worked  out  of  hard  wood.  The  outer  long  strip  and  the 
two  short  ones  are  slotted  to  receive  the  thumb-screws,  D,  D, 
shown  in  the  cut.  These  thumb-screws  pass  through  the  slots 
into  the  slab.  The  long  strip  in  the  center  is  also  slotted  and 
held  loosely  in  place  with  common  screws,  or  with  thumb-screws 
if  preferred.  The  inside  edges  of  all  these  strips  may  be  bev- 
elled slightly  towards  the  slab,  although  this  is  not  essential. 
The  slab  should  be  battened  at  the  ends  to  prevent  warping. 
It  should  also  be  smoothly  sand-papered  and  shellacked,  as  also 
the  strips.  The  dimensions  of  the  slab  will  vary  with  the  size 
and  number  of  the  plates  to  be  placed  on  it.  That  shown  in 
the  cut,  designed  to  hold  twelve  whole  plates  in  two  rows,  is  54 
inches  long  and  17  inches  wide.  The  slab  is  levelled  by  means 
of  the  screws  shown  in  Fig.  22. 

The  plates,  E,  E,  E,  are  placed  on  the  slab  between  the  strips 
as  shown,  the  movable  side  and  end  pieces  are  pushed  firmly 
against  the  plates,  and  thumb-screws  tightened.  The  plates 
are  then  coated,  using  the  coating-box  shown  in  Fig.  26,  and 
allowed  to  set.  When  set.  they  may  be  removed  by  loosening 
the  thumb-screws  and  taking  away  the  movable  strips,  as  the 
slots  are  cut  through  to  the  inside  edges. 

If  a  number  of  these  slabs  are  provided,  one  can  be  levelled 
above  the  other,  and  a  large  number  of  plates  coated  in  a  short 


COATING   THE    PLATES.  113 

time.  This  arrangement  when  used  in  connection  with  the 
coating;box  has  but  one  disadvantage — that  of  slow  setting. 
This  ma}r  be  obviated  by  placing  between  the  strips  long  strips 
of  plate-glass,  slightly  narrower  and  shorter  than  the  width 
and  length  of  the  plates.  In  this  case  the  thickness  of  the 
movable  strips  must  be  increased. 

Coating-Box. — A  very  efficient  coater  is  shown  in  Fig.  26. 

3.  IN 


The  box  is  exactly  6-J  inches  wide,  for  coating  whole  plates. 
C  is  a  solid  double  inclined  plane.  The  outlet,  A,  is  made  by 
inserting  a  piece  of  cardboard  between  JB  and  0,  while  the  box , 
is  being  fastened  together.  A  piece  of  cloth  is  glued  over 
this  opening.  The  box  is  made  of  wood  firmly  fastened  with 
glue  and  screws,  and  well  shellacked  outside  and  in.  The 
emulsion  is  poured  in,  and  made  to  run  over  the  inclined  plane 
by  tilting  the  box. 

Other  Methods  of  Coating. — Plates  up  to  6£  by  8£  inches 
are  easily  coated  by  balancing  the  plate  on  the  thumb  and 
fingers  of  the  left  hand,  then  with  the  right  hand  pour  care- 
fully over  the  plate  the  exact  quantity  of  emulsion  necessary 
to  give  a  film  of  the  desired  thickness.  The  spreading  of  the 
emulsion  may  be  helped  by  using  a  glass  rod,  a  clean  camel's- 
hair  brush,  or  the  tip  of  the  little  finger.  The  plate  is  gently 
rocked  a  moment  to  equalize  the  film  and  then  placed  on  the 
levelling  slab  to  set. 

The  flowing  of  the  emulsion  will  be  greatly  helped  by  first 
passing  over  the  surface  of  the  plate  a  squeegee  muffled  in 
soft  flannel  and  moistened  in  warm  water. 

When  the  plates  have  received  a  substratum  of  water  glass, 
or  one  of  sugar,  the  emulsion  can  be  flowed  over  the  plate 
like  collodion. 


114  THE   PHOTOGRAPHIC   NEGATIVE. 

Some  operators  prefer  to  coat  the  plates  while  resting  on 
the  levelling  tripod  shown  in  Fig.  2±,  but  the  author  sees  no 
advantage  in  this  practice. 

Another  method  is  to  level  the  plate,  then  to  pour  on  the 
necessary  quantity  of  emulsion  which  is  equalized  with  a 
broad  camel's-hair  brush  used  for  this  purpose  only.  The 
brush  is  rapidly  drawn  over  the  surface  of  the  plate  in  all 
directions  to  secure  an  even  coating.  Brushes  used  for  this 
purpose  should  have  rubber  mountings,  if  those  mounted  in 
metal  be  used,  the  metal  must  be  well  shellacked.  This  is  a 
simple  and  expeditious  method. 

In  whatever  way  the  coating  is  done,  the  plates  must  be 
slightly  warmed  and  dusted  before  the  emulsion  is  poured  on. 

Quantity  of  Emulsion  Necessary  to  Cover  Various  Sizes 
of  Plates. — The  film  when  dry  must  have  a  certain  thickness 
in  order  to  give  sufficient  density  to  the  image.  The  only 
test  possible  in  the  coating-room  is  to  examine  the  films  when 
set,  by  transmitted  light.  If  the  outline  of  the  flame  of  the 
ruby  lamp  can  be  just  made  out  through  the  film,  the  coating 
is  all  right.  To  secure  this  result  it  is  best  to  cover  each 
plate  with  a  fixed  and  constant  quantity  of  emulsion,  using  a 
pipette,  or  a  horn  or  wooden  spoon  of  proper  size  for  each 
size  of  plate. 

The  following  table  gives  the  quantities  of  emulsion  neces- 
sary to  give  a  good  film  to  the  sizes  in  most  common  use : 

3}^  by    finches 1      dram 

4  by    5      inches 1J^  drams 

4}£  by    Clinches 2  to  3      drams 

5  by    8      inches 3  to  4      drams 

6^  by    8%  inches 4  to  5      drams 

8      by  10      inches 6  to  8      drams 

One  dram  of  emulsion  for  every  ten  square  inches  of  surface 
is  about  right. 

Drying. — When  set  the  plates  may  be  dried  by  any  of  the 
methods  described  in  Chapter  I. 

Packing  the  Plates. — Many  different  methods  of  packing 
the  prepared  plates.  The  writer  prefers  to  place  them  face  to 
face  in  packages  of  half-a-dozen,  well  wrapped  up  in  non- 
actinic  paper,  and  to  store  them  in  pasteboard  boxes,  also  well 
wrapped,  in  a  cool,  dry  place. 


CHAPTER  XL 

DEVELOPMENT,  FIXING,  ETC. 

THE  reader  is  referred  to  Chapter  II.  for  the  theory  of  de- 
velopment and  fixing.  What  follows  in  this  chapter  deals 
with  the  practical  manipulations  of  the  dark-room. 

Development. — Many  substances  possess  the  power  of  re- 
ducing salts  of  silver  to  the  metallic  state,  and  so  giving 
visibility  to  the  latent  image  impressed  by  the  action  of  light. 
Among  others,  mention  may  be  made  of  sulphate,  borate; 
phosphate,  and  tartrate  of  iron,  pyrogallic  acid,  hydrochinone, 
hydroxylamine,  resorcin,  and  pyrocatechin.  Of  these  the  sul- 
phate of  iron,  pyrogallic  acid,  and  hydrochinone  alone  have 
more  than  an  experimental  value.  Hydrochinone,  although 
a  powerful  reducer,  is  but  little  used  at  present,  owing 
to  its  high  cost.  The  oxalate  of  iron  and  pyrogallic  acid  are 
the  reducing  agents  now  in  most  common  use,  each  having  its 
advocates  and  each  its  own  place  in  photographic  work. 

The  oxalate  of  iron  developer  is  the  simplest,  the  cleanliest, 
and  the  easiest  to  work,  but  as  a  rule  it  does  not  work  well 
with  short  exposure ;  it  does  not  admit  of  so  wide  a  range  of 
modification  to  correct  errors  of  exposure  as  does  the  method 
with  pyrogallic  acid.  On  account  of  the  regularity  of  its  ac- 
tion, and  the  fact  that  it  does  not  stain  the  film  or  the  hands, 
it  is  perhaps  the  best  method  for  beginners. 

Pyrogallic  acid  is  more  powerful,  has  a  wider  range  of 
modification  to  adapt  it  to  the  varying  needs  of  the  operator, 
and  seems  to  give  better  modeling  and  a  more  perfect  ren- 
dering of  half  tones.  It  is  the  method  for  the  advanced  prac- 
titioner, whose  judgment  has  been  ripened  by  long  experi- 
ence 


116  THE  PHOTOGRAPHIC  NEGATIVE. 

FORMULAE. 

Oxalate  of  Iron  Developers. 
1.— TRUTAT'S  FORMULA. 

a      Neutral  oxalate  of  potash 30      parts 

Water 100      parts 

b.  Sulphate  of  iron  30      parts 

Tartaric  acid %  part 

Water 100      parts 

Solution  b  will  keep  indefinitely  if  placed  in  a  strong  light 
when  not  in  use. 

c.  Bromide  of  potassium. 5  parts 

Water 100  parts 

This  is  the  restrainer,  and  is  to  be  used  only  in  cases  of  over- 
exposure. 

To  make  the  developer  add  one  part  of  b  to  three  or  four 
parts  of  a.  If  the  plate  proves  to  have  been  over-exposed,  add 
ten  drops  of  c  to  each  ounce  of  developer.  Develop  until  the 
image  is  visible  at  the  back  of  the  plate. 

The  proportions  of  one  to  three,  given  above,  are  the  strong- 
est possible  with  this  form  of  developer,  and  for  full  exposures 
will  prove  too  powerful.  A  safer  method  is  to  cover  the  plate 
first  with  a  mixture  of  four  parts  of  b  and  one  hundred  parts 
of  a. 

If  the  high  lights  begin  to  appear  in  one  or  two  minutes, 
the  exposure  was  about  right,  and  the  plate  is  removed  to  a 
second  tray  containing  twelve  parts  of  b  to  one  hundred  parts 
of  a,  in  which  the  development  is  completed.  If,  however, 
the  image  is  slow  in  appearing  in  the  first  solution,  it  is  an 
evidence  of  a  short  exposure,  and  the  plate  is  transferred  to 
the  second  tray,  and  after  a  few  moments  to  a  third  contain- 
ing the  normal  developer — b  twenty-five  parts,  a  seventy-five 
parts.  If  even  this  strong  developer  does  not  bring  out  suffi- 
cient detail,  pour  the  developer  into  a  graduate  containing  a 
few  drops  of  a  very  dilute  solution  of  hyposulphite  of  soda 
(1  to  2,000),  and  return  to  the  plate.  The  effect  is  almost 
instantaneous,  a  slight  veil  comes  over  the  image,  but  new  de- 
tails appear.  If  too  much  of  the  accelerator  be  added  the 
veiling  becomes  too  pronounced  and  the  plate  is  ruined.  The 
addition  of  hypo  is  always  dangerous. 


DEVELOPMENT,    FIXING,    ETC.  117 

2.— EDER'S  CONCENTRATED  DEVELOPER. 

Neutral  oxalate  of  potash 2      ounces 

Water 6      drams 

Sulphate  of  iron 3J£  ounces 

Dissolve  the  bxalate  in  boiling  water ;  when  dissolved  add 
the  iron  and  keep  at  200  deg.  until  dissolved.  Set  aside  for 
twenty-four  hours,  then  decant  the  clear  liquid  for  use. 

This  forms  a  very  powerful  developer   for   instantaneous 
views,  but  should  be  diluted  somewhat  with  water. 
3.— EDER'S  OXALATE  DEVELOPER. 

a.  Neutral  oxalate  of  potassium 100  parts 

Distilled  water 400  parts 

Acidulate  with  oxalic  acid 

b.  Sulphate  of  iron 50  parts 

Distilled  water 150  parts 

Sulphuric  acid 3  drops 

c.  Bromide  of  potassium 5  parts 

Distilled  water 50  parts 

d.  Hyposulphite  of  soda 1  part 

Distilled  water 100  parts 

For  the  developer  take  of  a  three  parts,  of  I  one  part.  Ee- 
strain  with  a  few  drops  of  c. 

For  over-exposures  take  less  of  J,  adding  more  if  re- 
quired. To  give  density  use  c. 

For  soft,  harmonious  negatives  full  of  detail  take  of 

a 2)^  ounces 

b %  ounce 

c 4      drops 

d 6      drops 

4.— FERROUS    OXALATE   DEVELOPER   WITH   CITRIC   ACID    FOR     INTENSE 
(BLACK  AND  WHITE)  NEGATIVES. 

a.  Water 500  parts 

Sulphate  of  iron .150  parts 

Citric  acid 2  parts 

b.  Water ...500  parts 

Neutral  oxalate  of  potassium 200  parts 

Solution  b  is  boiled,  and  when  cold  filtered  from  the  green 
crystals  which  may  have  separated  out.  One  part  of  a  is 
mixed  with  four  parts  of  b  to  form  the  developer. 


118  THE   PHOTOGRAPHIC   NEGATIVE. 

5.— OXALATE  DEVELOPER  WITH  CHLORIDE  OF  AMMONIUM  AND  CITRIC  ACID 
FOR  WELLINGTON'S  CITRO-CHLORIDE  EMULSION. 

a.  Oxalate  of  potassium 2  ounces 

Chloride  of  ammonium 40  grains 

Water 20  ounces 

b.  Sulphate  of  iron 4  drams 

Citric  acid 2  drams 

Water 20  ounces 

c.  Bromide  of  potassium 1  ounce 

Water 3  ounces 

Mix  a  and  5  in  equal  volumes,  and  add  one  dram  of  c  to 
each  ounce  of  developer. 

Alkaline  Development. — In  all  alkaline  developers  there  are 
three  elements :  1,  pyrogallic  acid,  or  its  equivalent ;  2,  an 
alkali ;  3,  bromide  of  potassium  or  ammonium. 

The  process  of  development  will  be  better  understood  if  we 
consider  the  office  which  each  of  these  elements  fills  in  devel- 
opment. This  will  enable  the  operator  to  compound  and  mod- 
ify his  developing  solutions  to  suit  his  tastes  and  needs. 

Pyrogallic  acid  is  a  powerful  absorbent  of  oxygen,  and  re- 
duces the  soluble  salts  of  silver  to  the  metallic  state ;  it  is  then 
the  reducing  agent  in  most  alkaline  developers.  Its  place  may 
be  supplied  by  other  oxygen  absorbers,  such  as  hydrochinone, 
hydroxylamine,  etc. 

Owing  to  its  reducing  power,  due  to  its  affinity  for  oxygen, 
pyrogallic  acid  gives  density  to  the  image.  If  the  amount  of 
alkali  used  remains  constant,  the  density  will  be  proportioned 
to  the  amount  of  acid  used.  The  degree  of  density  conferred 
is  governed  by  the  amount  of  pyro  used,  although  an  in- 
crease of  the  alkali  may  serve  the  same  purpose. 

The  alkali,  either  ammonia  or  the  carbonates  of  potash  or 
soda,  combines  with  the  bromide,  which  is  set  free  from  the 
silver  by  the  reducing  power  of  the  pyro.  If  the  amount  of 
alkali  be  increased,  there  is  a  corresponding  increase  of  the 
affinity  of  pyro  for  oxygen,  and  in  consequence  a  greater  re- 
ducing action,  giving  an  increased  amount  of  reduced  silver, 
which  may  increase  density.  Hence  an  increase  of  alkali 
means  increased  rapidity  of  development.  If  an  excess  of 


DEVELOPMENT,    FIXING,    ETC.  119 

alkali  be  added  the  reduction  of  silver  takes  place  so  rapidly  as 
to  produce  fog. 

Soft,  harmonious  images  are  produced  by  the  use  of  a  com- 
paratively large  proportion  of  alkali,  the  pyro  being  kept 
slightly  under  strength. 

On  the  other  hand  an  excess  of  pyro  gives  great  density  and 
heightens  the  contrasts  between  the  tones  of  the  image. 

The  bromide  diminishes  the  affinity  of  pyro  for  oxygen, 
and  hence  acts  as  a  restrainer.  It  also  diminishes  the  liability 
of  the  pyro  attacking  the  unaltered  bromide  of  silver,  and  thus, 
to  a  certain  extent,  prevents  fog. 

The  use  of  bromide  is  not  always  necessary,  since  gelatine 
itself  acts  as  a  restrainer,  by  holding  the  particles  of  silver  en- 
closed in  a  semi-impervious  coating,  which  presents  more  or 
less  resistance  to  the  action  of  the  developer. 

This  brief  explanation  of  the  function  of  each  of  the  com- 
ponents of  an  alkaline  developer  will,  it  is  hoped,  enable  the 
operator  to  compound  his  developed  with  judgment,  and  to  use 
it  with  discretion,  modifying  it  by  increasing  the  proportions  of 
one  or  the  other  ingredient  as  need  may  arise. 

The  question  now  arises :  Should  the  mixed  developer  be 
applied  at  once  to  the  plate,  or  should  the  pyro,  the  alkali,  or 
the  bromide  be  first  used  ? 

If  the  time  of  exposure  were  always  correct,  there  can  be  no 
doubt  that  the  best  method  would  be  to  apply  the  mixed  de- 
veloper. But  the  exposure  is  always  more  or  less  doubtful ;  it 
is  nearly  always  necessary  to  modify  the  developer  in  one  way 
or  another,  to  meet  special  needs. 

It  would,  then,  seem  more  scientific  to  begin  with  a  part  of 
the  developer,  and  to  add  the  other  ingredients  in  small  quan- 
tities as  required.  Since  the  effect  of  a  preliminary  applica- 
tion of  pyro  is  to  slow  the  plate,  the  author's  practice  is  to 
flood  it  first  with  a  solution  containing  about  half  the  quantity 
of  pyro  likely  to  be  needed,  and  to  add  the  alkali  in  small  in- 
crements, as  required  to  bring  out  detail,  finishing  up  with  the 
rest  of  the  pyro,  to  give  density,  using  the  bromide  only  in 
cases  of  necessity.  This  is  for  time  exposures. 

For  instantaneous  exposures  the  method  is  reversed ;  the 


120  THE   PHOTOGRAPHIC   NEGATIVE. 

plate  is  first  flooded  with  a  weak  solution  of  the  alkali,  and  the 
other  ingredients  added  as  required. 

In  this  connection  it  may  be  stated  that  the  author's  prefer- 
ence is  for  slow  development,  as  giving  the  operator  time  to 
see  the  needs  of  the  plate  and  meet  them  before  it  is  too  late. 
Hasty  development  has  ruined  many  a  plate  which  might  have 
been  saved  by  a  more  judicious  treatment. 

The  development  should,  as  a  rule,  be  continued  until  the 
image  is  fairly  visible  at  the  back  of  the  plate. 

Density. — Excess  of  pyro  or  prolonged  development  will 
increase  density.  The  amount  of  density  which  it  is  desirable 
to  give  to  the  image,  depends  on  the  nature  of  the  surfaces  on 
which  the  positive  is  to  be  printed,  since  negatives  adapted  to 
one  kind  of  surface  are  not  always  suitable  for  others.  For 
instance,  the  negative  which  will  give  good  results  on  albu- 
menized  paper,  will  not  necessarily  produce  equally  good 
prints  on  matt  surfaces,  as  the  platinotype,  bromide,  and  plain 
papers.  t 

For  printing  on  albumenized  paper,  the  negative  should  show 
all  the  detail  in  the  shadows  and  be  of  moderate  density,  since 
albumenized  paper  renders  the  most  delicate  gradations.  For 
matt  prints,  and  photogravures  or  heliogravures,  however,  there 
should  be  as  little  deep  shadow  as  possible  in  the  negative,  and 
a  small  amount  of  high  light,  not  more  than  one-fourth.  Most 
of  the  tones  should  be  half-tones,  subdued  lights,  and  well-illu- 
minated shadows,  with  great  opacity  in  the  high  lights,  for 
photo-engraving  purposes,  and  not  too  intense  for  matt  surface 
prints,  which  do  not  render  well  details  in  the  deepest  shadows. 

The  amount  of  density  must  then  be  determined  by  circum- 
stances, and  the  operator  will  seek  to  give  his  negatives  those 
special  qualities  which  best  fit  them  for  the  purposes  to  which 
they  are  to  be  put. 

The  Quantity  of  Pyro  and  Alkali  to  be  Used. — Excess  of 
pyro  or  alkali  is  equally  disastrous,  the  first  producing  too 
great  density,  the  latter  giving  foggy  images.  While  it  is  im- 
possible to  give  any  exact  proportions,  the  author,  after  com- 
paring many  formulae,  finds  that  two  and  a  half  grains  of  pyro 
'and  four  grains  of  carbonate  of  potash,  or  ten  grains  of  car- 


DEVELOPMENT,    FIXING,    ETC.  121 

bonate  of  soda,  or  two  drops  of  ammonia,  to  each  ounce  of 
mixed  developers,  is  a  fair  average.  In  special  cases  the  pyro 
may  be  increased  to  five  grains  to  the  ounce,  but  the  quantity 
of  alkali  should  not  greatly  exceed  the  quantities  given,  or  fog 
may  result. 

It  is  hoped  that  these  remarks  may  make  the  intelligent  use 
of  the  following  developers  more  easy. 

PYROGALLIC  ACID  DEVELOPERS. 
No.  1. — COOPER'S  FORMULA. 

a.  Sulphite  of  soda 6  ounces 

Water. . .    1  quart 

When  dissolved  add 

Pyrogallic  acid 1  ounce 

b.  Carbonate  of  soda,  pure 4  ounces 

Water 1  quart 

Developer :  a  1  ounce ;  5  1  ounce ;  water  1  ounce.  Restrain 
with  bromide  of  potassium. 

No.  2. — BEACH'S  FORMULA. 
A. — Pyro  Solution. 

Warm  distilled  water 2  ounces 

Sulphite  of  soda 2  ounces 

When  dissolved  and  cool  add 

Sulphurous  acid 2  ounces 

Pyrogallol %  ounce 

B.— Potash  Solution. 

1. — Water 4  ounces 

Carbonate  of  potash,  c.  p B  ounces 

2._Water Bounces 

Sulphite  of  soda 2  ounces 

Combine  1  and  2  into  one  solution. 

For  a  shutter  exposure  take  3  ounces  water,  -|  ounce  A,  and 
3  drams  B,  increasing  the  latter  to  5  drams  if  the  image  hangs 
back. 

For  over-exposure  3  ounces  water,  3  drams  A,  1  dram  B, 
adding  more  if  necessary. 


122  THE   PHOTOGRAPHIC   NEGATIVE. 

No.  3.— THE  AUTHOR'S  FORMULA. 

a.  Water 10  ounces 

Sulphite  of  soda 1  ounce 

Dissolve  and  add 

Pyrogallic  acid , 1  ounce 

Sulphuric  acid 20  drops 

b.  Water 10  ounces 

Carbonate  of  pytash 1  ounce 

c.  Water 10  ounces 

Carbonate  of  soda 1  ounce 

NORMAL  DEVELOPER. 

Water 4  ounces 

Solution  a 3  drams 

Solution  b. 2  drams 

Solution  c 2  drams 

These  quantities  may  be  increased  if  necessary.  An  excess 
of  J  over  c  gives  soft  harmonious  negatives  full  of  detail ;  when 
c  is  in  excess  more  density  and  less  detail  is  gained. 

No.  4. — CARBUTT'S  FORMULA. 

a.  Distilled  water 10  ounces 

Sulphite  of  soda 4  ounces 

Dissolve  and  add  slowly 

Sulphuric  acid 1  dram 

Pyrogallic  acid 1  ounce 

And  water  to  make  16  fluid  ounces. 

b.  Granulated  carb.  of  potash 2  ounces 

Granulated  carb.  of  soda 2  ounces 

Water 10  ounces 

Dissolve  and  add  water  to  make  16  fluid  ounces. 

NORMAL  DEVELOPER. 

Water 4  ounces 

Solution  a 3  diams 

Solution  b 2  drams 


DEVELOPMEHT,    FIXING,   ETC.  123 

No.  5.— EDWARDS'  FORMULA. 

a.  Pyrogallic  acid 1  ounce 

Glycerine 1  ounce 

Alcohol 6  ounces 

b.  Bromide  of  potassium 60  grains 

Ammonia 1  ounce 

Glycerine    6  ounces 

Water Bounces 

NORMAL  DEVELOPER. 

a.  Solutiona 1  part 

Water 15  parts 

b.  Solution  b 1  part 

Water 15  parts 

Mix  equal  parts  of  a  and  I.  If  the  image  flashes  up  quickly 
pour  off  the  mixed  developer,  and  flood  the  plate  with  solu- 
tion a. 

No.  6.— HENDERSON'S  FORMULA,  WITH  FERRO-CYANIDE  OF  POTASSIUM. 

Saturated  solution  of  ferro-cyanide  of  potassium.  ..10  ounces 

Ammonia 10  drops 

Pyrogallic  acid 15  grains 

This  solution  keeps  well.  If  it  refuses  to  develop  add  a  few 
drops  of  ammonia. 

No.  7. — E.  VON  SOTHEN'S  HYDROCHINONE  DEVELOPER. 

a.  Carbonate  of  soda 60  grains 

Water 1  ounce 

b.  Hydrochinone 12  grains 

Sulphite  of  soda 60  grains 

Water 1  ounce 

NORMAL  DEVELOPER. 

Water 1  ounce 

Solution  a I  ounce 

Solution  6 2  ounces 

The  mixed  developer  can  be  used  many  times. 
No.  8.— DR.  MARTELL'S  SODA,  POTASH,  AND  AMMONIA  DEVELOPER. 

a.     Pyrogallic  acid  1  dram 

Citric  acid 5  grains 

Sulphite  of  soda 1  dram 

Water 10  ounces 


2  THE   PHOTOGRAPHIC   NEGATIVE. 

b.  Carbonate  of  potash 1  ounce 

Water 20  ounces 

c.  Bromide  of  ammonium 15  grains 

Ammonia 1  dram 

Water 20  ounces 

NORMAL  DEVELOPER. 
a,  b,  and  c equal  parts 

NOTES  ON  THE  GrENEEAL  COMPOSITION  OF  DEVELOPERS. 

The  Oxalate  of  Iron  Developer. — In  this  developer,  com- 
monly known  as  the  ferrous-oxalato  developer,  the  only  func- 
tion of  the  oxalate  of  potash  is  to  produce,  when  combined  with 
sulphate  of  iron,  the  powerful  reducing  agent,  oxalate  of  iron, 
which  is  a  compound  insoluble  in  water,  but  soluble  in  an  ex- 
cess of  oxalate  of  potash.  If,  on  the  addition  of  the  iron  solu- 
tion to  the  oxalate  of  potash,  the  oxalate  of  iron  is  thrown 
down  in  the  shape  of  a  yellowish  powder,  it  is  a  sure  indication 
that  there  is  a  deficiency  of  the  oxalate  of  potash.  In  this  case 
the  developer  must  be  rejected  and  a  fresh  one  mixed,  contain- 
ing less  iron. 

The  oxalate  of  potash  must  be  neutral  or  slightly  acid. 
If  the  oxalate  solution  shows  an  alkaline  reaction,  turning  red 
litmus  paper  blue,  oxalic  acid  must  be  added  to  restore  the  red 
color  to  the  paper. 

The  sulphate  of  iron  solution  does  not  keep  well  unless  tar- 
taric  acid  is  added  ;  the  solution  must  then  be  kept  in  the  sun. 

Old  oxalate  of  iron  developer  may  be  kept  in  good  condi- 
tion by  the  occasional  addition  of  a  few  grains  of  tartaric  acid 
and  keeping  it  in  the  sun.  Old  developer  is  useful  to  start 
development  with. 

Alkaline  Developers. — In  this  form  of  developer  the  pyro 
is  the  reducing  agent,  the  other  ingredients  are  either  accelera- 
tors, restrainers,  or  preservatives  added  to  prevent  the  too 
rapid  deoxidation  of  the  pyro. 

When  using  pyro  the  author  prefers  to  begin  with  a  devel- 
oper weak  in  pyro  and  alkali,  adding  more  of  each  as  re- 
quired. Plates  known  to  have  received  a  full  exposure  should 


DEVELOPMENT,    FIXING,    ETC.  125 

be  soaked  for  two  or  three  minutes  in  a  plain  pyro  solution, 
adding  the  accelerator  in  small  quantities. 

Potash,  soda,  and  ammonia  are  accelerators ;  sulphite  of 
soda  is  a  preservative,  and  bromide  of  potassium  a  restrainer. 

Excess  of  pyro  gives  great  density  with  little  detail ;  excess 
of  accelerator  gives  plenty  of  detail  but  little  density.  Bear- 
ing these  principles  in  mind  the  intelligent  operator  is  able  to 
modify  his  developer  to  suit  special  cases. 

The  Hydrochinone  Developer. — This  form  of  developer  is 
but  little  known,  owing  chiefly  to  its  expensiveness,  hydro- 
chinone  being  manufactured  only  in  small  quantities. 

Its"  many  good  qualities,  however,  should  recommend  it. 
It  is  a  more  powerful  reducer  than  pyro,  but  slower  and  more 
uniform  in  its  action  ;  it  does  not  oxidize  as  quickly  as  pyro  ; 
it  gives  a  velvety  black  image  with  great  cleanness  in  the 
shadows,  and  it  does  not  stain.  For  transparencies  and  opals 
it  is  far  superior  to  pyro  or  oxalate  of  iron. 

The  Alum  Bath. — When  the  development  is  completed, 
the  negative  should  be  immersed  for  five  minutes  in  a  five 
per  cent,  solution  of  alum.  This  hardens  the  film,  thus  pre- 
venting frilling,  and  in  the  case  of  pyro-developed  negatives, 
removes  any  coloration  of  the  film  caused  by  the  oxidation  of 
the  pyro. 

The  alum  bath  may  be  used  for  many  negatives,  but  the 
same  bath  must  not  be  used  both  for  iron  and  pyro-developed 
negatives. 

Fixing. — The  negative  is  washed  slightly  after  leaving  the 
alum  bath,  and  fixed  in  a  one  to  five  hyposulphite  of  soda 
solution.  It  should  remain  in  this  bath  for  some  time  after 
the  creamy  appearance  has  left  the  plate. 

Washing. — In  order  to  eliminate  thoroughly  all  traces  of 
hypo,  the  plates  must  receive  a  thorough  washing  in  many 
changes  of  water,  or,  better  still,  in  running  water. 

The  different  methods  of  washing  will  be  found  described 
in  Chapter  II. 

When  the  negatives  are  thought  to  be  sufficiently  washed,  a 
small  quantity  of  the  drainings  should  be  placed  in  a  beaker 


126  THE   PHOTOGRAPHIC   NEGATIVE. 

and  tested  for  hypo,  using  for  that  purpose  the  following  solu- 
tion : 

Permanganate  of  potash 2  grains 

Carbonate  of  potash 20  grains 

Water 40  ounces 

The  addition  of  a  few  drops  of  this  rose-colored  solution  to 
a  pint  of  water  will  produce  a  slightly  pink  tinge.  If  any 
hypo  be  present  this  color  will  give  place  to  one  of  a  slightly 
greenish  hue. 

If  this  test  detects  hypo  the  washing  must  be  prolonged,  or 
the  plates  may  be  immersed  for  a  short  time  in  the  following 
hypo-eliminator : 

BELLITZKI'S  HYPOCHLORITE  OF  ZINC — HYPO-ELIMINATOR. 

a.  Chloride  of  lime -..  .304  grains 

Water 35  ounces 

b.  Sulphate  of  zinc 610  grains 

Water 100  ounces 

Add  J  to  a  and  shake  well. 

Set  aside  for  some  hours  and  decant  the  clear  liquid,  which 
must  be  kept  in  well-stoppered  bottles.  It  retains  its  good 
qualities  as  long  as  it  smells  of  hypochlorous  acid. 

For  use  add  one  part  of  the  solution  to  sixty  parts  of  water. 

After  this  treatment  the  plate  is  washed  for  ten  minutes, 
all  adhering  spects  removed  with  a  soft  sponge,  and  dried 
spontaneously. 

Intensifying. — Many  negatives  are  wanting  in  density  ow- 
ing to  over-exposure  or  insufficient  development.  In  such 
cases  intensification  must  be  resorted  to  in  order  to  increase 
the  density.  The  bichloride  of  mercury  intensifier  in  its  com- 
mon form  will  be  found  in  Chapter  II.  It  is,  perhaps,  as 
good  as  any. 

If  preferred,  one  of  the  following  formulae  may  be  sub- 
stituted for  it. 

Dr.  Eder's. — The  negative  is  whitened  in  a  saturated  solu- 
tion of  bichloride  of  mercury,  and  after  thorough  rinsing  im- 
mersed in 

Potassium  cyanide 10  parts 

Potassium  iodide 5  parts 

Mercuric  chloride 5  parts 

Water 2000  parts 

and  well  washed. 


DEVELOPMENT,    FIXING,    ETC.  127" 

Cyanide  of  Silver  Method. — The  negative  is 
whitened  in  the  following  : 

Bichloride  of  mercury 10  grains 

Chloride  of  ammonium 10  grains 

Water 1  ounce 

It  is  then  well  washed  and  blackened  in 

a.  Cyanide  of  potassium 2  ounces 

Distilled  water 48  ounces 

b.  Nitrate  of  silver 1  ounce 

Distilled  water 6  ounces 

Mix  a  and  5  by  pouring  5  gradually  into  a  with  constant 
stirring.  Allow  the  mixture  to  stand  a  few  days  before  using. 

The  Gallic  Acid  and  Nitrate  of  Silver  Intensifier. — Dr. 
Wallace  and  Mr.  Bartlett  have  recently  worked  out  a  modifi- 
cation of  an  old  wet  plate  intensifier  which  makes  it  applic- 
able to  gelatine  emulsion  plates. 

The  author  has  found  it  reliable  and  efficient. 

The  following  solutions  may  be  kept  in  stock : 

1.  Perchloride  of  iron 4  grains 

Chrome  alum 2  grains 

Citric  acid 4  grains 

Water 1  ounce 

2.  Gallic  acid 80  grains 

Alcohol 1  ounce 

3.  Nitrate  of  silver 40  grains 

Water 1  ounce 

For  use  add  one  dram  each  of  2  and  3  to  two  or  three 
ounces  of  water. 

The  negative  is  soaked  for  a  few  minutes  in  solution  1,  in 
which  it  should  not  be  allowed  to  bleach  unless  it  is  slightly 
fogged  or  over-developed. 

The  plate  is  then  rinsed  under  the  tap,  and  sufficient  of  solu- 
tions 2  and  3  diluted  as  directed,  is  flowed  over  it  and  allowed 
to  act  until  the  proper  degree  of  density  is  reached.  After 
which  it  is  well  washed. 

This  method  is  applicable  either  before  or  after  fixing.  In 
either  case  the  negative  must  be  well  washed. 

Uranium  Intensifier. — The  plate  is  flooded  with  a  one  per 


128  THE   PHOTOGRAPHIC   NEGATIVE. 

cent,  solution  of  nitrate  of  uranium.  After  remaining  on  the 
plate  for  a  minute  it  is  poured  back  into  the  graduate,  in 
which  a  few  drops  of  a  two  per  cent,  solution  of  ferricyanide 
of  potassium  have  been  placed.  The  mixture  is  then  poured 
back  on  the  plate.  If  this  does  not  give  sufficient  density  add 
more  of  the  ferricyanide. 

This  is  one  of  the  most  permanent  of  intensifies. 

Reduction. — It  occasionally  happens  that  negatives  have 
too  great  density.  In  this  case  the  density  must  be  reduced. 
This  may  be  done  with  either  of  the  following  solutions  : 

FARMER'S  REDUCER. 

Ferricyanide  of  potassium  (saturated  solution) 1  part 

Hyposulphite  of  soda  solution  (one  to  five) 10  parts 

BELLITZKI'S  REDUCER. 

Potassium  ferric  oxalate 1  to  10  grains 

Hyposulphite  of  soda  solution  (one  to  five) 1  ounce 

Local  reduction  can  be  made  by  mixing  the  preparations 
with  mucilage  and  applying  with  a  brush.  Wash  well  after 
treatment. 

Varnishing. — All  negatives  worth  preserving  should  be 
varnished.  The  method  of  applying  the  varnish  will  be  found 
on  page  30.  A  few  additional  formulae  are  given  here  : 

1.  Sandarac ^ 4  ounces 

Alcohol 28  ounces 

Oil  of  lavender 8  ounces 

Chloroform 5  drams 

2.  White  hard  varnish 15  ounces 

Methylated  alcohol 25  ounces 

This  will  be  found  a  good  and  cheap  varnish  if  durability 
is  not  required,  as  it  is  easily  rubbed  up  for  retouching  upon 
and  easily  cleaned  aff.  Yery  suitable  for  enlarged  negatives 
that  are  not  to  be  retained. 

TOUGH,  HARD,  AND  DURABLE. 

3.  Shellac 1^  ounces 

Mastic ^  ounce 

Oil  of  turpentine Bounce 

Sandarac .......  1 J^  ounces 

Venice  turpentine J^  ounce 

Camphor 10      grains 

Alcohol  , 20     fluid,  ounces 


DEVELOPMENT,    FIXING,    ETC. 


129 


4.  Sandarac  .  .    ..........  .  ........................  90  ounces 

Turpentine  ....................................   36  ounces 

Oil  of  lavender  .................................   10  ounces 

Alcohol  ........................................  500  ounces 

This  one  may  be  nibbed  down  with  powdered  resin  to  give 
a  good  retouching  surface  : 

5.  Sandarac  ....................................  4      ounces 

Seed  lac  .......................................  1      ounce 

Castor  oil  ....................................  3      drams 

Oil  of  lavender  ................................  1J£  drams 

Alcohol  ...................................  ,  .  .  .18     ounces 

COLLODION  VARNISH. 

6.  Tough  pyroxyline  ................................  12  grains     • 

Alcohol  ..........................................   1  ounce 

Ether  ...........................................   1  ounce 

Flow  over  the  plate  as  in  collodionizing,  drain  well,  and 
dry. 


CHAPTEE  XII. 

PIPER   NEGATIVES.      STRIPPING   FILMS   ON   PAPER,   CARDBOARD,   AND 
COLLODION. 

THE  latest  development  in  photographic  negatives  is  a  return 
to  first  principles,  the  use  of  paper  as  a  permanent  or  tem- 
porary support  for  the  sensitive  film. 

It  is  not  the  writer's  intention  to  enter  into  a  discussion  of 
the  advantages  or  disadvantages  of  the  new  method.  The 
writer's  own  opinions  on  the  subject  are  decided  and  based  on 
practical  experience  in  the  field  and  in  the  dark-room,  but  he 
is  content  to  keep  those  opinions  to  himself,  simply  giving  de- 
tailed descriptions  of  the  manipulations  peculiar  to  the  use  of 
paper  or  other  similar  support  as  a  substitute  for  glass. 

For  various  reasons  collodion  does  not  seem  to  take  kindly 
to  paper ;  therefore  it  is  to  be  assumed,  of  all  the  methods  here 
given,  that  the  sensitive  film  is  formed  by  coating  the  paper 
with  one  of  the  emulsions  given  in  chapter  VIII. 

The  use  of  paper  as  the  support  does  not  necessitate  any 
change  in  the  nature  of  the  emulsion,  except,  perhaps,  that  a 
slight  increase  in  the  quantity  of  gelatine  may  be  advisable,  or 
a  decrease  in  the  amount  of  water. 

Any  changes  which  are  recommended  are  necessitated  by 
the  flexible  nature  of  the  support,  and  the  somewhat  different 
conditions  under  which  the  emulsion  must  be  flowed  over  it. 
.  Radical  differences  exist  between  the  preliminary  manipula- 
tions of  paper  intended  as  a  permanent  support,  and  those  to 
be  employed  when  the  film  is  to  be  finally  removed  from  the 
paper. 

Each  of  these  will  be  treated  in  turn,  beginning  with  those 
to  be  used  when  the  paper  is  to  form  the  permanent  support. 

The  Paper. — When  the  paper  is  to  form  the  final  support 
of  the  negative,  great  care  must  be  taken  to  select  a  variety 


PAPER   NEGATIVES.  131 

presenting  the  greatest  uniformity  of  surface,  and  freedom 
from  grain.  The  kind  known  as  plain  Saxe  negative  paper  is 
well  adapted  to  this  process.  Parchment  paper,  if  it  could  be 
had  free  from  marks  and  lines,  would  be  the  best,  since  its  use 
would  render  the  after  operation  of  oiling  unnecessary. 

Whatever  brand  of  paper  be  selected,  its  right  side  is  the 
one  to  be  coated.  Neglect  of  this  precaution  will  result  in 
grainy  and  spotted  negatives,  due  to  the  unevenness  of  the  un- 
polished side  of  the  sheets. 

Sizing  the  Paper. — If  the  paper  selected  be  strongly  sized, 
it  may  be  coated  without  further  preparation.  Better  results, 
however,  will  be  obtained  on  paper  which  has  received  a  coat- 
ing of  coagulated  albumen  or  insoluble  gelatine.  Both  of  these 
may  be  obtained  of  any  dealer  in  materials  for  the  carbon 
process,  or,  if  preferred,  the  experimenter  may  prepare  his 
own  paper,  by  floating  it  for  a  minute  on  the  following  bath  : 

Hard  gelatine   4  ounces 

Sulphate  of  baryta  (powdered) 2  ounces 

Water 20  ounces 

Dissolve  and  mix  thoroughly  ;  then  stir  in  a  hot  solution  of 
six  grains  of  chrome  alum  in  one  ounce  of  water. 
.  The  paper  is  coated  by  rolling  it  up  tightly,  face  outwards  ; 
the  roll  is  laid  upon  the  surface  of  the  liquid,  the  loose  end  is 
seized  and  the  paper  unrolled ;  it  is  then  hung  up  to  dry. 

Paper  possessing  a  high  degree  of  transparency  may  be  pre- 
pared by  soaking  the  sheets  for  some  days  in  copal  varnish,  and 
then  drying.  When  dry  the  surfaces  are  polished  with  pum- 
ice stone,  after  which  a  layer  of  soluble  glass  is  applied  and 
well  rubbed  in  with  a  piece  of  cloth.  Some  small  experiments 
of  the  author  in  this  direction  have  resulted  favorably,  the 
emulsion  readily  flowing  over  the  prepared  surface. 

Coating  the  Paper. — The  prepared  sheets  may  be  coated 
with  the  emulsion  by  the  method  just  described,  having  been 
first  slightly  dampened.  The  tray  containing  the  emulsion  is  ' 
placed  in  a  larger  tray  containing  water,  the  temperature  of 
which  is  kept  at  about  70  deg.  The  paper  is  rolled  up  as  be- 
fore and  floated  on  the  emulsion,  avoiding  air  bells.  It  is  then 
seized  by  one  end  and  drawn  over  the  edge  of  a  glass  plate, 


132 


THE   PHOTOGRAPHIC   NEGATIVE. 


previously  levelled  over  the  tray.  As  soon  as  the  film  is  set 
the  paper  may  be  stripped  from  the  glass  and  hung  up  to  dry. 
Another  very  good  method  is  that  sometimes  used  in  the 
preparation  of  carbon  tissue,  and  shown  in  Fig.  28.  The  des- 
cription of  the  apparatus  is  from  "  Abney's  Treatise  on  Pho- 


FIG. 


tography."  A  porcelain  or^other  dish,  A,  is  placed  on  a  hot 
water  tin,  B,  the  water  being  kept  at  the  boiling  point  by  a 
lamp  or  Bunsen  burner.  Over  the  dish  is  placed  a  level  table, 
D,  at  one  end  of  which  is  a  roller,  G,  that  is  on  a  level  with 
the  top  surface  of  a  glass,  E,  placed  on  the  table,  D.  The 
paper,  F,  is  floated  on  the  warm  gelatine  solution  contained  in 
the  dish,  drawn  through  it,  seized  by  the  hands,  drawn  over 
the  roller  on  to  the  plate,  E,  where  it  is  allowed  to  remain  till 
the  gelatine  is  well  set ;  after  which  it  is  hung  up  by  clips  to 
dry.  The  dish  has  to  be  removed  each  time  that  paper  is 
floated  ;  if  B  be  widened,  the  dish  can  be  run  backwards  and 
forwards  in  a  very  simple  manner. 

Another  simple  method  is  to  soak  the  paper  in  warm  water 
until  limp,  then  to  place  it  on  a  glass  plate,  and  with  blotting- 
paper  and  a  squeegee,  to  remove  all  excess  of  moisture.  The 
paper  may  then  be  coated  as  if  it  were  a  glass  plate.  After 
being  coated  it  is  placed  on  the  levelling  slab  until  the  film  is 
well  set,  after  which  it  may  be  hung  up  to  dry,  or  allowed  to 
dry  on  the  glass. 


PAPER   NEGATIVES.  133 

This  is  the  simplest  method,  and  for  most  purposes  it  will  be 
found  as  good  as  any. 

Another  method,  which  is  preferred  by  some  operators,  is  to 
coat  a  glass  plate,  previously  polished  with  French  chalk,  with 
the  emulsion,  and  when  the  film  has  thoroughly  set,  gently  to 
squeegee  the  moistened  sheet  of  paper  in  perfect  contact  with 
the  film.  When  dry,  the  paper  bearing  the  film  may  be  pulled 
from  the  glass. 

A  glass  roller  may  be  used  to  equalize  the  film.  This  roller 
is  made  by  inserting  corks  in  the  ends  of  a  piece  of  glass  tub- 
ing, one-half  inch  in  diameter,  and  a  trifle  longer  than  the  width 
of  the  paper  to  be  coated.  About  one-eighth  of  an  inch  from 
each  end  rubber  bands  surround  the  rod.  These  serve  to  keep 
the  rod  slightly  above  the  surface  of  the  paper,  and  their  thick- 
ness determines  that  of  the  film.  Short  pieces  of  wire  are  in- 
serted in  the  corks,  the  ends  of  a  bent  wire  are  bent  around 
these  wires,  to  form  a  handle  by  which  the  rod  is  manipulated. 

The  emulsion  is  poured  on  the  paper  in  parallel  lines  between 
the  rod  and  the  handle ;  the  rod  is  then  drawn  backwards  and 
forwards  over  the  paper  to  equalize  the  film. 

The  glasses  on  which  the  sheets  of  paper  are  squeegeed  must 
be  a  trifle  wider  than  the  paper,  in  order  that  the  rubber  bands 
may  rest  on  the  glass.  The  distance  between  the  bands 
should  just  equal  the  width  of  the  paper. 

The  emulsion  may  also  be  spread  over  the  paper  with  a  stiff 
brush. 

Balagny^s  Method. — M.  Balagiiy  prefers  to  paste  the  paper 
to  the  glasses,  over  which  has  been  flowed  a  thin  film  of  the 
following  solution  : 

Benzine '. . .  3J^  ounces 

Gum  dammar 15      grains 

White  wax 30      grains 

Resin 15      grains 

This  solution  is  flowed  over  the  glass  like  collodion  and  the 
glass  is  racked  away  to  dry. 

The  paper,  cut  to  size,  is  first  soaked  in  water  till  limp,  and 
then  given  an  even  coating  of  thin  starch  paste,  free  from 
lumps,  and  laid  down  on  the  glass,  the  starched  side  of  the 


134:  THE   PHOTOGRAPHIC   NEGATIVE. 

paper  in  contact  with  the  waxed  surface  of  the  glass.  The 
face  of  the  paper  is  then  covered  with  a  sheet  of  blotting- 
paper,  and  all  excess  of  paste,  as  well  as  all  air-bells,  removed 
with  the  squeegee.  When  dry,  the  paper  is  coated  and  the 
film  allowed  to  dry  on  the  glass ;  the  paper  is  then  stripped 
from  the  glass  by  raising  one  corner  first. 

The  advantage  of  this  method  is  that  the  paper  is  kept  in 
perfect  contact  with  the  glass,  on  which  it  is  tightly  stretched, 
and  that  there  is  no  possibility  of  its  cockling  or  rolling  up  as 
it  dries. 

STRIPPING  FILMS.     PAPER  SUPPORT. 

Chennemere's  Method. — The  glasses  are  waxed  as  in  Balag- 
ny's  method  given  above.  The  paper  is  cut  somewhat  smaller 
than  the  plates,  softened  in  water,  and  laid  down  on  the  plate, 
leaving  a  narrow  margin  of  glass  on  all  sides.  Excess  of  mois- 
ture and  air-bells  are  removed  by  means  of  blotting-paper  and 
the  squeegee.  Narrow  strips  of  albumen  paper  are  then 
pasted  around  the  paper  and  glass,  and  when  dry  the  paper  is 
given  a  thin  coating  of  French  chalk,  all  excess  being  removed 
with  a  camel's-hair  brush,  and  then  collodionized  with  the 
following  plain  collodion : 

Ether 1%  ounces 

Gun-cotton    15      grains 

Alcohol 1%  ounces 

Castor  oil 10      drops 

As  soon  as  the  collodion  is  dry  the  paper  is  coated  and 
allowed  to  dry  on  the  glass.  It  can  then  be  stripped  from  the 
glass  by  cutting  along  the  edges  of  the  albumen  paper. 

The  only  disadvantage  of  the  above  method  is  the  liability 
of  the  films  to  leave  the  paper  when  cut  down  to  smaller  sizes. 
To  obviate  this  difficulty,  M.  Chenneviere  has  introduced  the 
following  improvement:  The  paper  is  given  a  coating  of  a 
waxing  solution  made  as  follows : 

White  wax  . .  •. 61      grains 

Benzine 3J^  ounces 

This  is  applied  with  a  piece  of  linen  dipped  in  the  solution. 
The  paper  when  dry  is  dampened  and  fastened  to  the  glass  as 


PAPER   NEGATIVES.  135 

before.     It  is  then  collodionized,  and  when  again  dry  coated 
with  the  emulsion. 

Balagny's  Method. — The  paper  is  pasted  on  the  glass  as 
described  on  page  133,  and,  when  dry,  is  polished  with 
French  chalk,  a  moderately  thick  coating  being  given  in  order 
to  fill  the  pores  and  leave  a  smooth  surface.  It  is  then  collo- 
dionized with  the  following  plain  collodion : 

Pyroxyline 23      grains 

Alcohol 3      ounces 

Ether 4%  ounces 

When  dry,  the  paper  is  coated  as  usual  and  allowed  to  dry 
on  the  glass. 

Fdbrds  Method. — Plain  paper  of  good  body  is  given  a  coat- 
ing of  Para  gum  dissolved  in  benzine  (gum  30  grains,  benzine 
3  ounces),  and  hung  up  to  dry  in  a  place  free  from  dust. 

When  dry  it  is  moistened  and  squeegeed  into  perfect  contact 
with  a  glass  plate  previously  waxed  as  in  M.  Chenneviere's 
method,  coated  as  usual,  and  stripped  from  the  glass  as  soon  as 
the  film  has  set,  and  then  hung  up  to  dry. 

The  rubber  solution  must  be  well  filtered  through  several 
thicknesses  of  muslin,  and  it  is  conveniently  applied  to  the 
paper  with  a  brush,  placing  the  paper  on  a  glass  plate  and 
giving  it  a  thin  coating. 

Milsom's  Method  with  Waxed  Paper. — The  paper  is  cut 
one-half  an  inch  longer  and  wider  than  the  glass  supports.  It 
is  then  soaked  for  five  minutes  in  water,  and  then  pasted  by 
its  edges  on  its  glass  support.  For  this  purpose  the  paper  is 
laid  down  on  moist  blotting-paper,  with  the  side  to  be  coated 
in  contact  with  the  paper.  The  glass  plate  is  then  placed  over 
the  paper,  the  edges  of  the  latter  are  then  turned  over  and 
glued  or  pasted  to  a  sheet  of  common  paper  of  the  proper  size. 
Dry  between  blotters  under  moderate  pressure. 

When  dry  place  the  glass  on  a  metal  plate  warmed  to  above 
the  melting  point  of  wax.  With  a  piece  of  white  wax  go 
carefully  over  the  entire  surface  of  the  paper  until  it  is  evenly 
waxed  and  no  air- bells  remain  between  the  paper  and  the  glass. 
Then  remove  the  glass  from  the  metal  plate  and  remove  all 


136  THE   PHOTOGRAPHIC   NEGATIVE. 

excess  of  wax  by  gently  rubbing  with  a  piece  of  clean  flannel. 
The  glasses  are  then  dried  under  pressure,  the  waxed  surfaces 
being  placed  in  contact.  When  dry,  coat  as  usual. 

Eastman's  Method. — The  paper  is  first  coated  with  a  plain 
gelatine  solution  containing  15  to  20  grains  of  soft  gelatine  to 
the  ounce  of  water.  When  dry,  the  paper  is  again  coated 
with  any  good  emulsion  which  has  been  made  insoluble  by  the 
addition  of  chrome  alum. 

To  every  500  parts  of  emulsion  15  to  20  parts  of  the  follow- 
ing alum  solution  is  added  : 

Chrome  alum 4  parts 

Water 90  parts 

Glycerine 40  parts 

An  emulsion  containing  chrome  alum  should  all  be  used  at 
once. 

Stripping  films  on  Cardboard  Supports. — Any  of  the 
methods  described  above,  for  preparing  paper  to  serve  as  a  tem- 
porary support,  may  be  employed  when  cardboard  is  used. 

The  simplest  method  is  to  polish  the  cardboards  with  French 
chalk,  and  after  dusting  off  all  excess  of  chalk  to  collodionize 
them  with  any  good,  plain  collodion,  the  formula  given  on  page 
50  will  answer.  The  prepared  cards  are  thoroughly  soaked  in 
water,  and  then  squeegeed,  collodion  side  uppermost,  on  glass 
plates  somewhat  larger  than  the  cards.  The  edges  are  secured 
to  the  glass  with  gummed  paper,  and  when  dry  the  cards  are 
coated  as  usual. 

If  preferred,  the  cards  may  be  waxed  with  the  solution  given 
on  page  51,  before  collodionizing,  or  they  may  be  given  two 
coats  of  shellac. 

Balagny's  Method  with  Methyl  Alcohol. — To  obviate  the 
difficulty  of  determining  the  proper  point  at  which  to  cease 
the  development  of  films  on  paper  or  cardboard,  owing  to  the 
impossibility  of  judging  of  their  density  by  transmitted  light, 
M.  Balagny  has  worked  out  a  method  which  gives  films  which 
leave  their  support  when  placed  in  the  developer. 

Glass  plates  are  polished  with  French  chalk,  dusted  off,  and 
coated  with  any  good  emulsion. 


PAPER   NEGATIVES. 


137 


When  dry  the  films  are  collodionized  with  the  following 
collodion  : 


Ether 

Methyl  alcohol. 

Pyroxyline 

Castor  oil. . . 


.  3%  ounces 
.  3%  ounces 
.  30  grains 
,  1  dram 


The  paper  or  card  supports  are  moistened  in  water,  placed 
upon  a  clean  glass,  and  all  excess  of  moisture  removed 
with  blotting-paper  and  the  squeegee,  both  sides  being  thus 
treated.  A  ten  per  cent,  solution  of  pure  gum  is  then 
laid  on  with  a  brush,  after  which  the  paper  or  card  is 
carefully  laid  down  on  the  prepared  plate  and  squeegeed  into 
contact. 

As  soon  as  the  support  is  dry  it  is  stripped  from  the  glass  by 
cutting  around  the  edges  with  a  sharp  knife,  and  pulling  the 
paper  or  card  from  the  glass. 

After   exposure   these   films  are  soaked  for   three  or  four 
minutes  in  a  one  per  cent  chrome  alum  solution,  then  in  pure 
water  until  the  film  begins  to  wrinkle.     It  is  then  carefully  re- 
moved from  its  support  and  placed  in  the  developer. 
c  c c 


FIG.  29. 

Figure  29  shows  a  coating-board,  devised  by  the  author,  for 
coating  cards.  It  has  been  found  useful  for  holding  the  cards 
while  being  waxed  or  polished  and  collodionized,  as  well  as 
while  being  coated.  It  will  also  answer  for  holding  paper. 

A  is  a  half-inch  slab  of  hard- wood,  battened  at  the  ends  to 
prevent  warping,  planed  and  sand-papered  perfectly  smooth. 
Its  length  and  breadth  are  a  trifle  in  excess  of  the  size  of  the 
cards  or  paper  to  be  coated. 


138  THE   PHOTOGRAPHIC  NEGATIVE. 

B,  B,  B,  B,  are  movable  half-inch  strips  of  thin  metal  well 
shellacked  or  japanned,  and  having  slots  cut  in  them,  as  shown. 
C,  C,  C,  are  ordinary  flat-headed  screws,  which  serve  to  clamp 
the  metal  strips.  The  slab  is  levelled  with  levelling  screws  or 
wedges. 

The  paper  or  cards  to  be  coated  are  first  cut  somewhat  larger 
than  the  size  desired,  moistened  in  water  and  laid  smoothly  on 
the  slab  from  which  the  metal  strips  have  been  removed.  All 
excess  of  moisture  is  removed,  and  perfect  contact  secured 
with  blotting  paper  and  the  squeegee.  The  strips  are  then 
placed  in  position  and  tightly  screwed  down,  in  which  con- 
dition they  act  as  clamps  to  hold  the  paper  tightly  stretched. 
If  the  paper  is  to  serve  as  a  permanent  support,  the  emulsion 
is  poured  on  immediately,  and  evenly  distributed  with  a  glass 
rod,  the  ends  of  which  rest  on  the  side  strips,  which  determine 
the  thickness  of  the  film. 

If  stripping  films  are  desired,  the  paper,  or  cards,  when  dry, 
is  polished  and  collodionized  as  described  above,  and  then 
coated. 

"When  the  films  are  set  the  paper  may  be  removed  from  the 
slab  and  hung  up  to  dry.  The  author,  however,  prefers  to  al- 
low the  film  to  dry  on  the  slab. 

PELLICULAK  FILMS  WITHOUT  SUPPORT. 

Balagny's  Method, — Clean  glass  plates  are  polished  with 
French  chalk,  dusted,  and  collodionized  with  the  plain  collo- 
dion given  on  page  135,  and,  when  dry,  coated  with  an  emulsion 
containing  35  ounces  of  water  and  1080  grains  of  gelatine  for 
every  770  grains  of  nitrate  of  silver. 

When  the  films  are  dry  they  may  be  detached  from  the 
glass  by  cutting  around  the  edges,  first  detaching  one  corner 
from  the  plates. 

These  films  will  be  strong  enough  to  undergo  all  the  neces- 
sary manipulations. 

Another  method  of  preparing  films  without  support,  is  to 
polish  and  collodionize  the  plates,  then  to  paste  narrow  strips 


PAPER   NEGATIVES.  139 

of  pasteboard  around  their  edges,  and  to  coat  them  with  the 
following  gelatine  solution : 

Water 14  ounces 

Hard  gelatine 1,080  grains 

Soak  the  gelatine  in  cold  water,  dissolve,  and  add 

Water 3%  ounces 

Chrome  alum 7      grains 

Glycerine 1      dram 

Ferric  acid 40      drops 

This  is  to  be  added  in  a  fine  stream,  with  constant  stirring. 
The  mixture  is  then  well  filtered,  and  the  plates  coated.  When 
dry  they  are  coated  with  the  emulsion,  and  the  dried  films  are 
stripped  from  the  glass,  as  in  the  preceding  method. 

The  author  sees  no  great  advantage  in  these  two  methods 
over  the  usual  stripping  processes.  They  are  given  to  demon- 
strate the  possibility  of  preparing  a  sensitive  film,  having  all 
the  transparency  of  glass,  without  its  bulk  or  weight. 

Methods  of  Exposing  Films  on  Paper  Supports. — Many 
methods  of  exposing  films  on  flexible  supports  have  been  de- 
vised. Most  of  those  recently  put  forth  for  gelatine  films  are 
as  old  as  the  calotype  process,  and  possess  few  or  no  claims  to 
novelty. 

For  the  exposure  of  emulsion  paper,  in  long  rolls,  the  roll- 
holder,  in  some  one  of  its  modern  forms,  is  certainly  the  best 
method  for  the  tourist  who  does  not  care  to  develop  his  ex- 
posures until  he  returns  home. 

The  stay-at-home  photographer,  however,  who  only  exposes 
a  plate  now  and  then,  and  develops  it  at  once,  will  use  simpler 
and  less  expensive  methods,  better  suited  to  his  needs. 

Many  forms  of  film-carriers  are  now  in  the  market,  of  which 
the  best  known,  perhaps,  is  the  Eastman,  which  consists  of  a 
thin  tablet  of  wood  surrounded  by  a  light  detachable  metal 
frame,  in  which  the  sensitive  tissue,  cut  to  size,  is  laid  face 
down,  and  the  back-board  placed  in  position,  when  the  whole 
is  introduced  into  the  plate-holder,  exactly  as  if  it  were  the 
usual  plate. 


140  THE   PHOTOGRAPHIC  NEGATIVE. 

Another  effective  method  is  to  coat  thin  pieces  of  shellacked 
wood  with  the  following  mixture : 

Water 4      ounces 

Sulphate  of  baryta 2J£  ounces 

Sugar 1      ounce 

Gelatine 1      ounce 

Glycerine 6      ounces 

The  wooden  tablets  are  levelled  and  given  a  thin  coating  of 
the  mixture,  which  may  be  applied  with  a  brush.  The  sensi- 
tive film  is  laid  down  on  one  of  the  prepared  tablets,  and  gently 
smoothed  into  contact.  It  is  easily  removed  for  development, 
and  the  prepared  tablets  will  answer  for  several  exposures. 

Still  another  method  is  to  gum  the  tissues  by  the  edges  to  a 
glass  plate,  a  thin  wooden  tablet,  or  a  piece  of  stiff  cardboard. 

A  fourth  method,  applicable  to  single  holders,  is  to  place 
the  tissue  between  a  clean  glass  plate  and  a  sheet  of  cardboard. 
If  this  method  be  employed,  care  must  be  taken  to  allow  for 
the  thickness  of  the  glass  in  focusing.  The  best  method  seems 
to  be  that  adopted  in  the  Vergara  double  holder,  in  which  the 
sensitive  tissue,  cut  to  twice  the  length  of  a  single  sheet,  is 
folded  across  the  middle,  and  the  end  of  the  septum  placed  in 
the  fold,  and  the  whole  slid  into  grooves  cut  in  the  holder. 

Films  on  cardboard  are  placed  in  the  holders  exactly  as  glass 
plates.  Pellicular  films  on  collodion  or  gelatine  are  best  ex- 
posed behind  a  glass  plate. 

Development. — The  development  of  films  on  paper  or  card- 
board supports  is  carried  out  precisely  as  in  the  case  of  glass 
plates,  using  any  of  the  developers  given  in  the  previous  chapter, 
preferably  the  oxalate  of  iron  developer,  or  those  modifications 
of  the  alkaline  developer  which  contain  oulphite  of  soda. 

Good,  full  exposures  give  the  best  results  with  stripping 
films.  Long  development  with  pyro  is  very  apt  to  tan  or 
harden  the  soft  gelatine  substratum,  owing  to  the  penetration 
of  the  developer  through  the  pores  of  the  paper,  and  so  make 
stripping  difficult  or  impossible. 

For  this  reason  most  of  those  who  make  use  of  stripping 
films,  adopt  the  oxalate  of  iron  (ferrous  oxalate)  developer. 

The  following  formulae   and   directions   are  those  recom- 


PAPER   NEGATIVES.  141 

mended  by  the  Eastman  Co.,  for  their  films,  but  they  will  be 
found  equally  applicable  to  others  : 

No.  1. 

Sulphite  sodium,  pure,  crystals 6  ounces 

Distilled  or  boiled  water,  cold 1  qt.  (32  ounces) 

Pyrogallic  acid 1  ounce 

Dissolve  the  sulphite  first  and  then  add  the  pyro. 

No.  2. 

Carbonate  soda,  pure J^  pound 

Water 1      quart 

To  develop,  pour  into  a  clean  tray  the  following  : 

No.  1. 1  ounce 

No.  2 1  ounce 

Water 1  ounce 

Immerse  the  exposed  film  in  a  tray  of  clean,  cold  water,  and, 
with  a  soft  camel's  hair  brush,  gently  remove  the  air  bells  that 
cling  to  the  surface  of  the  film.  As  soon  as  limp,  remove  the 
film  to  the  tray  containing  the  developer,  and  proceed  with  the 
development  the  same  as  with  a  dry  plate.  The  image  should 
commence  to  appear  in  ten  or  fifteen  seconds.  If  the  lights 
come  slowly  and  with  no  detail  in  the  shadows,  add  not  to  ex- 
ceed one  ounce  of  No.  2.  If  the  image  appears  too  quickly, 
add  ten  to  twenty  drops  of  the 

Restrainer. — 

Bromide  potassium 1  ounce 

Water 6  ounces 

Keep  this  in  a  dropping  bottle,  consisting  of  an  ordinary 
bottle  having  two  notches  cut  lengthwise  in  the  cork,  on  oppo- 
site sides. 

Oxalate  Developer. — The  oxalate  developer  works  well  with 
Eastman's  American  films,  and  it  has  no  tendency  to  attack 
the  soluble  substratum  and  render  it  insoluble. 

FORMULA. — No.  1. 

Oxalate  of  potash 1  pound 

Hot  water ...  .48  ounces 


Acidify  with  Oxalic  acid. 


142  THE    PHOTOGRAPHIC   NEGATIVE. 

No.  2. 

Proto-sulphate  of  iron 1  pound 

Hot  water 32  ounces 

Tartaric  acid 60  grains 

No.  3. 

Bromide  potassium 1  ounce 

Water 1  quart 

These  solutions  keep  separately,  but  must  be  mixed  only  for 
immediate  use. 

To  Develop. — Take  No.  1 ,  six  ounces ;  No.  2,  one  ounce  ; 
No.  3,  ten  drops.  Mix  in  the  order  given  ;  use  cold. 

After  exposure,  soak  the  paper  in  water  until  limp,  then 
immerse  in  the  developer. 

The  image  should  appear  slowly  and  should  develop  up 
strong,  clear,  and  brilliant.  When  the  lights  are  sufficiently 
developed,  wash  well  and  fix. 

After  fixing,  wash  in  three  or  four  changes  of  cold  water  for 
five  or  ten  minutes,  and  the  film  is  then  ready  for  transferring. 

When  the  oxalate  developer  is  used,  it  is  sometimes  advisable 
to  use  alum  in  the  fixing-bath,  to  prevent  frilling,  but  after 
using  it  the  paper  must  be  stripped  as  quickly  as  possible  after 
squeegeeing  on  to  the  glass ;  that  is  to  say,  after  standing 
thirty  minutes  under  pressure  and  before  it  becomes  entirely 
dry,  otherwise  the  substratum  will  become  insoluble. 

The  film  may  be  examined  from  time  to  time  by  transmitted 
light,  by  holding  it  up  by  the  corners.  When  sufficient  density 
is  obtained,  wash  the  film  in  two  changes  of  cold  water,  and 
then  immerse  in  the 

Fixing-Bath. — 

Hyposulphite  sodium 4  ounces 

Water , 1  pint 

Mix  fresh  fixing-bath  for  each  batch  of  negatives.  Use  no 
alum  in  the  fixing-bath. 

Films  fix  quicker  than  glass  dry  plates,  and  the  completion 
of  the  operation  can  be  ascertained  by  the  even,  translucent 
appearance  as  seen  from  the  back  while  lying  in  the  bath,  or 
by  examination  by  transmitted  light. 

Drying, — Paper  negatives,  if  not  to  be  stripped,  are  best 


PAPER   NEGATIVES.  143 

dried  on  a  piece  of  glass,  well  polished  with  French  chalk,  or 
on  a  sheet  of  ebonite.  The  negative  is  squeegeed  into  contact 
with  the  glass  or  ebonite,  and  allowed  to  dry  spontaneously. 
When  dry  it  will  peel  off  with  a  brilliant  gloss. 

Oiling. — Paper  negatives,  when  dry,  may  be  printed  from 
without  further  treatment.  It  is  better,  however,  to  render 
them  more  translucent  by  oiling  or  waxing.  Many  methods 
have  been  advocated  for  increasing  tranelucency. 

The  author  usually  adopts  the  following  method  :  The  nega- 
tive is  secured,  face  down,  to  a  clean  flat  board,  by  thumb  tacks 
at  the  corners.  The  oiling  medium,  castor  oil,  vaseline,  or 
translucine,  is  then  applied  to  the  back  ;  the  negative  is  then 
held  over  a  stove  and  kept  in  constant  motion  until  it  assumes 
a  uniform  dark  color.  It  is  then  allowed  to  cool,  and  a  second 
coat  of  oil  is  applied  and  heated  as  before.  All  excess  of  oil 
is  then  removed  with  a  piece  of  sponge  or  clean  rag. 

Retouching. — Paper  negatives  are  best  retouched  from  the 
back  after  oiling.  The  oiled  surface  takes  the  pencil  readily, 
and  any  amount  of  working  up  may  be  given  to  the  negative. 

Printing. — Lay  the  negative,  film  side  up,  on  a  clean  glass 
plate,  secure  the  corners  with  gummed  paper,  and  place  in  the 
printing  frame. 

Preserving  Paper  Negatives. — Place  a  sheet  of  oiled  paper 
between  the  backs  of  the  negatives  and  keep  under  pressure ; 
a  deep  printing  frame  makes  a  convenient  press. 

Intensification,  if  necessary,  should  be  done  before  the  nega- 
tives are  oiled. 

Stripping  Films. — The  development  of  films  which  are  to 
be  stripped  from  their  temporary  supports  is  the  same  as  that 
given  above  for  paper  negatives. 

After  development,  fixing,  and  washing,  they  are  prepared 
for  stripping  in  some  one  of  the  following  methods : 

Eastmarts  Method  for  "American  Films" — Coat  a  clean 
glass  plate,  one  size  larger  than  the  film,  with  the  following 
rubber  solution : 

Rubber  cement 1  ounce 

Benzine 9  ounces 

The  above  rubber  cement  is  such  as  sold  at  the  rubber  stores 


144  THE   PHOTOGRAPHIC   NEGATIVE. 

in  half-pound  cans  for  25  cents,  and  is  a  mixture  of  pure  rub- 
ber and  benzine.  This  article  should  not  be  mistaken  for  the 
bi-sulphide  of  carbon  and  rubber  cement  used  by  shoemakers. 
Allow  the  rubber  to  dry  until  "  dead,"  say  five  or  ten  min- 
utes, then  flow  with  plain  collodion  made  as  follows : 

Ether 1  ounce 

Alcohol 1  ounce 

Gun-cotton 12  grains 

As  soon  as  set,  wash  under  tap  until  greasy  lines  disappear, 
then  slide  the  prepared  glass  into  a  tray  of  water,  face  up, 
slide  the  fixed  and  washed  American  film  negative  into  the 
water  over  the  plate,  face  down,  grasp  together  by  the  edges 
and  draw  plate  and  negative  out  of  the  water,  allowing  to 
drain  from  one  end.  Carefully  squeegee  into  contact,  examin- 
ing from  front  for  air-bells,  place  under  blotter  and  weight  to 
dry  for  thirty  minutes  only,  then  slide  plate  supporting  the 
negative  into  a  pan  of  water  about  120  deg.  to  140  deg.  Fahr., 
raise  corner  of  paper  with  a  pin  and  pull  it  off,  or  slide  the 
paper  off  from  the  glass  sidewise,  using  gentle  pressure,  leav- 
ing the  negative  film  on  the  glass.  Brush  gently  with  camel's- 
hair  brush  dipped  in  warm  water,  transfer  plate  to  tray  of  cold 
water,  negative  side  up,  slide  a  gelatine  skin  of  the  proper  size 
into  water  over  negative,  rough  side  up,  allow  skin  to  soak 
one  minute,  then  grasp  together  with  plate,  and  lift  out  of  the 
water.  Squeegee  into  contact,  and  stand  to  dry.  When  thor- 
oughly dry,  flow  with  plain  collodion.  When  dry,  cut  around 
the  edges  and  peel  off  the  glass ;  remove  adhering  rubber  from 
the  face  of  the  negative  by  gently  rubbing  with  the  palm  of 
the  hand,  or  with  a  tuft  of  cotton  moistened  with  benzine. 

The  sheets  of  gelatine  are  soaked  for  five  minutes  in  the 
following  bath : 

Water 35      ounces 

Alcohol 2%  ounces 

Glycerine 2J£  ounces 

After  soaking,  a  gelatine  sheet  is  carefully  placed  on  the 
film  and  lightly  squeegeed  into  contact.  When  dry,  the  nega- 


PAPER   NEGATIVES.  145 

live  is  stripped  off  as  before.  It  is  advisable,  however,  to  col- 
lodionize  the  gelatine  backing  with  plain  collodion  before 
stripping. 

Chennemere's  Method.— Stripping-films  prepared  according 
to  M.  Chenneviere's  method  are  developed,  fixed  and  washed 
as  usual.  They  are  then  squeegeed  into  contact  with  glass 
plates  previously  polished  with  French  chalk  and  collodionized 
with  plain  collodion.  When  dry,  the  negatives  are  cut 
through  to  the  glass  near  the  edges  and  pulled  from  the  plates. 
The  film  is  separated  from  the  paper  by  inserting  a  knife-blade 
between  the  two  at  one  corner  and  pulling  them  apart. 

Fabrds  Method  for  Films  on  Paper  Coated  with  Rubber. — 
The  washed  negatives  are  squeegeed  into  contact  with  polished 
and  collodionized  glass  plates.  When  dry,  the  back  of  the  paper 
is  covered  with  benzine  and  rubbed  with  a  cloth  dipped  in 
benzine,  to  dissolve  the  rubber.  The  paper  is  then  removed, 
the  back  of  the  film  gently  rubbed  with  a  soft  cloth  dipped  in 
benzine,  to  remove  all  traces  of  rubber.  After  drying,  the 
films  are  coated  with  a  plain  collodion,  and,  when  again  dry, 
they  are  stripped  from  the  glass  as  usual,  first  cutting  around 
the  edges. 

This  method  is  applicable  to  all  films  united  to  paper  sup- 
ports with  wax  or  collodion,  as  in  the  methods  of  MM.  Balagny 
and  Milsom,  given  above. 

Films  on  Cardboard  Supports  are  developed,  fixed,  washed 
and  dried  like  glass  plates.  When  dry,  they  are  collodionized 
with  plain  collodion,  and,  when  again  dry,  stripped  from  the 
cardboard  support  by  inserting  the  point  of  a  knife-blade  be- 
tween the  film  and  card  at  one  corner  and  pulling  them  apart. 

The  films  are  then  placed  in  water  in  which  a  polished  glass 
plate  has  been  laid.  After  a  moment's  soaking,  the  collodion 
side  of  the  film  is  brought  in  contact  with  the  polished  side  of 
the  glass,  and  the  two  removed  from  the  tray.  Perfect  contact 
is  secured  with  the  squeegee,  and  the  film  allowed  to  dry. 
When  dry,  it  is  coated  with  plain  collodion,  and,  when  again 
dry,  stripped  from  the  glass  as  usual. 

Films  on  Gelatine  or  Collodion  Supports. — After  the  usual 
operations  of  development,  fixing,  and  washing,  M.  Balagny 


14:6  THE   PHOTOGRAPHIC   NEGATIVE. 

recommends  that  these  films  be  quickly  blotted  off  between 
clean  blotters.  They  are  then  immersed  for  five  minutes  in 
the  following  bath : 

Alcohol 16  ounces 

Glycerine 1  ounce 

They  are  then  removed  from  the  dish,  drained  for  half  a 
minute,  placed  between  clean  blotters  and  laid  down  on  a  glass 
plate.  A  piece  of  rubber  cloth  is  next  laid  over  the  blotters 
and  gently  pressed  with  a  roller,  to  remove  all  excess  of  mois- 
ture. This  process  is  repeated  three  or  four  times,  changing 
the  blotters  each  time.  The  films  are  then  dried  thoroughly 
between  fresh  sheets  of  blotting-paper. 

These  flexible  plates,  as  the  inventor  calls  them,  are  superior 
to  films  on  paper  or  cardboard,  in  that  they  allow  the  progress 
of  development  to  be  watched  by  transmitted  light. 

The  author,  however,  has  found  no  insuperable  difficulty  in 
judging  of  the  density  of  films  on  paper  or  cards  by  reflected 
light.  His  practice  is  to  develop  until  the  shadows  begin  to 
gray  over,  and  then  to  wash  and  fix  as  usual. 


CHAPTEK  XIII. 

FAILURES  IN  THE  GELATINO-BROMIDE  PROCESS. 

MOST  of  the  possible  causes  of  failure  with  this  process  with 
the  proper  remedies,  will  be  found  enumerated  in  this  chapter. 

Fluidity  of  the  emulsion  in  the  flask. — This  is  usually  due 
to  failure  to  add  an  antiseptic  to  the  emulsion.  Such  an  emul- 
sion will  not  set,  and  is  not  safe  to  use. 

Irregular  flowing  of  the  emulsion  is  most  commonly  due  to 
the  want  of  a  substratum,  and  may  be  corrected  by  applying 
any  of  the  substrata  given  in  Chapter  IV. 

Wavy  and  irregular  lines  during  coating  are  caused  by 
the  plates  being  too  cold,  or  the  emulsion  not  being  sufficiently 
fluid.  The  plates  should  be  warmed  slightly,  and  the  emulsion 
kept  at  a  temperature  of  about  95  deg. 

Refusal  of  the  emulsion  to  set  may  be  due  to  high  tempera- 
ture of  the  coating-room,  or  to  a  deficiency  of  gelatine  in  the 
emulsion,  or  to  a  decomposition  of  the  gelatine,  caused  by  long 
boiling,  excessive  use  of  ammonia,  or  frequent  re-meltings.  If 
the  defect  is  due  to  the  first  cause,  lower  the  temperature  of 
the  coating-room,  which  should  always  be  at  about  70  deg. 

If  the  gelatine  be  deficient,  add  25  or  30  grains  of  gelatine 
to  every  2  drams  of  emulsion,  and,  after  standing  for  a  few 
hours,  dissolve  in  the  water-bath. 

In  the  third  case  it  is  best  to  reject  the  emulsion. 

Spots  and  small  rings  are  due  to  the  irregular  drying  of  the 
plates.  The  door  of  the  box  or  room  in  which  the  plates  are 
dried  should  be  opened  as  little  as  possible  during  the  drying. 

Fog  is  due  to  several  causes,  as  over-exposure,  forced  devel- 
opment, admission  of  white  light,  or  too  long  an  exposure  to 
the  light  of  the  dark-room. 

If  the  edges  of  the  plate,  which  were  protected  by  the  re- 


14:8  THE   PHOTOGRAPHIC   NEGATIVE. 

bate  of  the  frame,  are  free  from  fog,  the  plate  was  over 
exposed. 

If  the  whole  plate  fogs  over  during  development,  it  is  either 
light-struck,  or  the  emulsion  was  fogged. 

This  point  may  be  determined  by  developing  and  fixing  an 
unexposed  plate.  If  this  shows  no  signs  of  fog,  the  camera  or 
the  slide  is  at  fault,  and  must  be  examined. 

Fog  on  unexposed  plates  may  be  due  to  some  fault  in  the 
making  of  the  emulsion,  or  to  the  slow  drying  of  the  plates. 

Fogged  emulsion  may  occasionally  be  made  fit  for  use  by  the 
addition  of  a  few  drops  of  tincture  of  iodine. 

Plates  which  have  been  coated  and  show  signs  of  chemical 
fog  should  be  soaked  in  the  following  bath  : 

Bichromate  of  potassium 1  part 

Hydrochloric  acid 3  parts 

Water 100  parts 

After  this  treatment  the  plates  are  well  washed  and  then 
dried. 

Yellow  fog  occurs  only  with  the  alkaline  developer ;  it  is 
due  to  the  staining  action  of  pyro  on  the  film,  and  may  be  re- 
moved by  soaking  the  plates,  after  fixing,  in  a  saturated  solu- 
tion of  alum,  to  which  one  per  cent,  of  hydrochloric  acid  lias 
been  added. 

lied  fog  is  caused  by  an  excess  of  nitrate  of  silver  used  in 
the  emulsion.  It  also  sometimes  occurs  when  the  plate  has 
been  long  subjected  to  the  action  of  a  concentrated  oxalate  of 
iron  developer. 

Green  fog  is  most  commonly  caused  by  an  excessive  amount 
of  ammonia  in  the  developer.  It  may  sometimes  be  removed 
by  soaking  the  plate  in  a  solution  of  peroxide  of  hydrogen. 

A  slight  green  fog  does  not  injure  the  printing  qualities  of 
the  negative.  If,  however,  the  fog  is  very  dense,  it  may  be 
cleared  away  by  converting  the  deposit  into  chloride  of  silver, 
by  means  of  perchloride  of  iron  solution,  to  which  a  trifle  of 
bromide  of  potassium  has  been  added,  and  an  after  re  devel- 
opment with  ferrous  oxalate.  If  the  original  deposit  chances 
to  be  too  feeble  for  printing,  expose  the  chloride  of  silver  de- 


FAILURES    IN    THE    GELATINO-BROMIDE   PROCESS.  149 

posit  to  day-light  before  re-developing,  which  will  increase  the 
density  very  much. 

A  white  opalescent  veil,  covering  the  film,  is  sometimes  met 
with  in  plates  developed  with  oxalate  of  iron,  when  lime  is 
present  in  the  water.  It  has  no  injurious  effect,  but  may  be 
removed  by  soaking  the  plate  in  dilute  hydrochloric  acid. 

A  yellow  deposit  forms  on  the  film  when  using  the  oxalate 
of  iron  developer,  owing  to  an  excess  of  sulphate  of  iron  hav- 
ing been  added  to  the  oxalate  of  potassium. 

Undefined  marks  and  spots  on  the  film  after  development 
are  due  to  grease  in  the  gelatine.  Emulsion  prepared  with 
ammonia  is  free  from  this  defect. 

Pinholes  are  caused  by  dust  on  the  plate. 

White  marks  or  round  spots  are  caused  by  air  bubbles  form- 
ing on  the  film  during  development.  This  may  be  prevented  by 
soaking  the  plate  in  water  before  developing,  or  by  keeping 
the  developer  in  motion. 

Lack  of  detail  is  caused  by  insufficient  exposure,  by  want  of 
sufficient  alkali  in  the  developer,  or  by  the  excessive  use  of  the 
restrainer. 

Want  of  density  is  due  to  over-exposure  or  to  the  use  of 
a  weak  developer. 

Excessive  density  is  caused  by  over-development. 

Halo  around  the  high  lights,  is  generally  due  to  the  reflec- 
tion of  light  from  the  back  of  the  plate.  It  may  be,  in  part 
prevented  by  backing  the  plate  with  some  non-reflecting  color, 
mixed  with  gum  water. 

Matt  surface  plates,  and  those  containing  iodide  of  silver, 
are  usually  free  from  this  defect. 

Frilling  of  the  film  during  development  is  most  commonly 
caused  by  the  use  of  soft  gelatine  in  the  preparation  of  the 
emulsion.  The  formation  of  frills  and  blisters  is  promoted  by 
the  addition  of  too  much  alkali  to  the  developer,  by  the  use  of 
warm  developers  and  wash-waters,  by  treating  the  plates 
with  dilute  acid  solutions  to  remove  fog  or  stains,  and  by  the 
use  of  a  concentrated  fixing-bath. 

Films  which  show  a  tendency  to  frill  should  be  treated  be- 
fore or  after  development  with  10  per  cent,  chrome  alum  solu- 
tion. 


150  THE   PHOTOGRAPHIC   NEGATIVE. 

Frills  showing  during  development  may  be  arrested  by  add- 
ing a  teaspoonful  of  saturated  solution  of  Epsom  salts  (sul- 
phate of  magnesia)  to  the  developer.  Plates  with  a  tendency 
to  frill  should  be  placed  in  the  alum-bath. 

The  best  remedy  for  frilling  is  to  work  in  a  low  tempera- 
ture. Let  the  amateur  defer  developing,  during  hot  summer, 
to  the  early  morning  hours,  if  he  has  no  means  of  lowering 
the  temperature  of  his  work-room  or  water  by  artificial  means. 

Soaking  in  alcohol  will  usually  remove  films  by  the  absorp- 
tion of  the  water  under  them. 

Slow  fixing  is  due  to  the  use  of  a  too  dilute,  or  too  concen- 
trated, hypo-solution  for  fixing.  The  proper  strength  is  1  to 
5.  Plates  containing  iodide  are  always  slow  to  fix. 

Spots  and  Stains  appear  on  the  films  when  intensified  with 
mercury,  owing  to  insufficient  washing  after  fixing,  or  after 
the  treatment  with  mercury. 

Red  stains,  which  appear  on  the  films  after  having  been 
printed  from,  are  caused  by  the  silver  in  the  paper,  combining 
with  the  gelatine.  They  can  sometimes  be  removed  by  soak- 
ing the  films  in  dilute  cyanide  of  potassium,  accompanied  by 
gentle  rubbing,  but  this  method  is  very  dangerous.  Dr.  Ehr- 
mann recommends  that  a  line  be  drawn  around  the  stains  with 
a  piece  of  wax  sharply  pointed ;  the  film  is  then  softened  in 
water,  and  the  spots  are  treated  with  cyanide  of  potassium 
solution  applied  with  a  fine  brush. 

Farmer's  or  Belitzki's  reducing  solutions,  given  on  page 
128,  may  also  be  applied  in  the  same  way. 

The  wax  is  removed  with  a  tuft  of  cotton,  moistened  with 
ether. 


CHAPTER  XIV. 

METHODS  OF  STRIPPING  FILMS  FROM  GLASS  PLATES. 

MOST  of  the  mechanical  printing  processes  require  reversed 
negatives  or  positives  for  the  production  of  the  printing 
plate. 

In  such  cases,  unless  a  reversed  negative  was  obtained  in  the 
camera,  by  the  use  of  a  reversing  prism,  or  by  exposing  through 
the  glass  support,  it  is  necessary  to  strip  the  film  from  the 
plate,  in  order  to  turn  it  and  print  from  the  reversed  side. 

The  use  of  stripping  films,  prepared  according  to  the  in- 
structions given  in  the  previous  chapter,  gives  negatives  which 
can  be  printed  from  either  side. 

A  few  of  the  best  methods  for  stripping  are  given  below. 

Collodion  Films. — The  plates  are  collodionized  without  be- 
ing given  a  substratum.  If  the  negatives  have  been  varnished, 
the  varnish  is  removed  by  pouring  over  them  sufficient  of  the 
following  solution  to  cover  them  well : 

Distilled  water 5      ounces 

Caustic  potash 120      grains 

Alcohol 17%  ounces 

The  alcohol  is  used  to  neutralize  the  destructive  effect  of 
the  alkali  on  the  film. 

As  soon  as  the  varnish  is  dissolved  the  negative  is  well 
washed  in  pure  water,  levelled,  and  coated  with  a  solution  of 
six  parts  of  gelatine  in  forty  parts  of  water,  to  which  from 
four  to  five  parts  of  alcohol,  and  from  one-half  to  one  part  of 
glycerine  have  been  added.  When  the  gelatine  has  thoroughly 
dried,  the  film  is  cut  around  the  edges  and  stripped  from  the 
glass. 

For  "  process  work  "  the  film  is  turned  by  coating  the  nega- 
tive, when  dry,  with  a  solution  of  Para  gum  in  benzine,  and 


152  THE   PHOTOGRAPHIC   NEGATIVE. 

afterwards  with  a  tough  collodion.  When  this  is  dry  the  film 
is  cut  as  before,  and  is  immersed  in  a  1  to  10  acetic  acid 
solution.  As  soon  as  the  film  floats  off  it  is  turned  upon 
another  glass  plate  placed  in  the  solution,  or  glycerine.  When 
again  dry,  the  film  may  be  pulled  from  the  glass  after  cutting 
around  its  edges. 

Gelatine  Films. — Unless  specially  prepared  for  stripping, 
gelatine  films  must  be  treated  with  a  20  per  cent,  chrome  alum 
solution,  for  at  least  one  hour,  and  then  immersed  in  a  20  per 
cent,  hydrofluoric  acid  solution  until  the  film  leaves  the  glass. 
A  polished  and  collodion ized  plate  is  placed  in  the  tray,  under- 
neath the  film,  and  both  removed  from  the  water,  and  laid 
down  on  a  plain  surface.  A  piece  of  sheet  gelatine,  previously 
soaked  in  water,  containing  2  per  cent,  of  glycerine  is  then 
brought  in  contact  with  the  film,  and,  when  dry,  the  film 
is  easily  detached  from  the  glass. 

A  better  method  is  to  prepare  the  plates  for  stripping  before 
they  are  coated.  This  is  easily  done  by  polishing  them  with 
French  chalk,  and  collodionizing  them  with  a  plain  collodion 
containing  1  per  cent,  of  pyroxyline,  first  taking  the  precau- 
tion to  remove  the  chalk  from  the  edges  of  the  plate,  for  about 
an  eighth  of  an  inch,  with  a  wad  of  cotton  wool,  dipped  in 
albumen.  The  plates  are  then  coated  with  the  emulsion. 

To  effect  the  transfer  it  is  only  necessary  to  cover  the  film 
after  fixing,  and  washing  with  water  containing  2  per  cent,  of 
glycerine,  and  then  .to  lay  over  it  a  piece  of  sheet  gelatine, 
previously  soaked  in  the  same  glycerine  solution.  The  whole 
is  then  covered  with  a  piece  of  rubber  cloth,  and  gently 
squeegeed. 

When  the  gelatine  sheet  is  dry  it  is  collodionized,  dried,  and 
stripped,  as  described  on  page  144. 


CHAPTEK  XY. 

COLOR-SENSITIVE    PLATES. 

Isochrotnatic  or  Orthochromatic  Methods. — The  ordinary 
photographic  plate,  whether  prepared  by  any  of  the  well- 
known  albumen,  collodion,  or  gelatine  methods,  is  deficient  in 
its  power  of  giving  proper  tone-value  to  the  different  colors. 
It  does  not  render  them  with  the  same  relative  force  with 
which  they  impress  themselves  upon  the  retina.  Some  colors 
appear  too  dark  ;  others  too  light  in  the  finished  print. 

Prof.  Draper  was  the  first  to  discover  the  fact  that  only  the 
absorbed  rays  produce  chemical  changes  in  a  sensitive  surface. 

The  knowledge  of  this  fact  was  the  starting  point  in  the 
search  for  substances  which  should  make  sensitive  plates  prop- 
erly color-sensitive,  by  conferring  upon  them  the  property  of 
translating  the  different  colors  of  the  spectrum  into  their  true 
values  in  light  and  shade. 

In  this  connection  special  mention  is  made  of  Angerer, 
Eder,  Obernetter,  Scolik,  Mallmann,  Ducos  du  Hauron,  Cros, 
Tailfer,  Josef  Albert,  Schumann,  Yogel,  Ives,  Ehrmann, 
Abney,  and  Bierstadt,  as  investigators  of  this  somewhat  ob- 
scure branch  of  photography. 

As  the  result  of  these  investigations,  it  is  now  possible  to 
prepare  sensitive  plates  which  will  render,  with  great  fidelity, 
the  varying  intensities  of  different  colors. 

The  method  is  of  great  value  in  the  reproduction  of  oil 
paintings,  water-colors,  colored  fabrics,  and,  in  general,  of  all 
objects  in  which  there  is  a  large  proportion  of  red  and  yellow 
rays. 

The  problem  to  be  solved  was  a  method  of  treating  emul- 
sions or  prepared  plates,  which  should  increase  their  absorp- 
tion for  rays  which  are  but  feebly  absorbed  by  ordinary 
plates. 


154  THE  PHOTOGRAPHIC  NEGATIVE. 

Two  methods  were  found  available  to  effect  this  result,  one 
being  to  color  the  emulsion  with  certain  dyes,  the  other,  and 
more  practical,  being  to  bathe  plates,  prepared  as  usual,  with  a 
dilute  solution  of  the  same  dyes. 

It  was  also  found  necessary  to  interpose  between  the  sensi- 
tive surface  and  the  lens,  or  to  place  in  front  of  the  lens,  col- 
ored screens  in  order  to  modify  the  action  of  the  light  to 
adapt  it  to  the  work  it  was  called  upon  to  perform. 

Of  the  dyes  most  commonly  used  in  the  preparation  of 
color-sensitive  plates,  those  belonging  to  the  eosine  group  have 
given  the  best  results.  Chinoline,  and  many  others  too  numer- 
ous to  mention,  have  also  been  successfully  employed  by  dif- 
ferent experimenters. 

Without  attempting  to  discuss  the  subject  exhaustively,  it  is 
intended  to  give  sufficiently  detailed  instruction,  drawn  from 
the  best  sources,  to  enable  the  intelligent  operator  to  produce 
good  results. 

The  Light  Screen.— The  light  reflected  from  the  object  to 
be  reproduced  is  passed  through  a  colored  glass  screen  before 
falling  upon  the  sensitive  plate,  in  order  to  equalize  the  chem- 
ical action  of  different  colored  rays.  The  shade  and  depth  of 
color  of  this  screen  are  somewhat  varied  to  adapt  it  to  special 
needs.  The  color  in  most  common  use  is  yellow,  but  the 
color  is  often  modified  to  suit  the  prevailing  tints  of  the  ob- 
ject to  be  reproduced.  In  many  cases  a  slight  tinge  of  red, 
blue,  or  green  is  advisable.  Such  screens  are  easily  prepared 
by  coating  a  piece  of  clean  plate-glass,  free  from  scratches  and 
bubbles,  with  a  plain  collodion,  to  which  sufficient  of  some 
yellow  dye  has  been  added  to  impart  the  desired  tint — aurantia 
or  dimethyl  orange  and  tincture  of  Bengal  curcuma  answer 
well  for  this  purpose. 

Ives  prefers  to  use  a  plate-glass  cell,  filled  with  a  solution  of 
bichromate  of  potash. 

Some  experimenters  strip  the  colored  collodion  film  from 
the  glass,  cut  it  to  the  size  and  shape  of  the  lens,  and  mount 
it  with  the  lens  in  the  tube.  The  screen  may  be  placed  in 
front  of  or  behind  the  lens.  In  many  cases,  especially  where 
the  object  is  lighted  by  yellow  light,  the  screen  may  be  dis- 
pensed with. 


COLOR-SENSITIVE   PLATES.  155 

The  use  of  the  screen  materially  lengthens  the  time  of  ex- 
posure, which  can  only  be  learned  by  practice. 

Color-Sensitive  Gelatine  Emulsion. — Gelatine  emulsion 
may  be  made  color-sensitive  by  the  addition  of  eight  drops  of 
a  one  to  500  eosine  solution  to  every  three  and  a  half  drams 
of  emulsion.  Cyanine,  erythrosine,  chinoline,  or  other  dyes 
maybe  used. 

Color-Sensitive  Bath-Plates. — Tailfer,  in  France ;  Schu- 
mann, Angerer,  in  Austria ;  Ives,  Bierstadt  and  Ehrmann,  in 
America,  were  the  first  to  demonstrate  the  possibility  of  ren- 
dering ordinary  gelatine  plates  color-sensitive  by  immersion  in 
a  batli  of  the  dye-stuff. 

This  method  is  superior  to  the  older  one  of  adding  the  dye 
to  the  emulsion,  and  it  is,  therefore,  to  be  preferred,  both  on 
account  of  its  simplicity,  certainty,  and  a  general  excellence. 

Scolik's  Method,  with  Erythrosine. — 

1.— PREPARATORY  BATH. 

Water 7  ounces 

Ammonia 35  drops 

The  plates  are  immersed  for  two  minutes  in  this  bath,  to 
secure  an  even  action  of  the  color-bath,  and  to  increase  sensi- 
tiveness. 

2.— COLOR  BATH. 

Erythrosine  solution  (one  to  one  thousand) 7      drams 

Ammonia 1      dram 

Distilled  water 6J^  ounces 

The  plates  are  bathed  in  this  solution  from  sixty  to  ninety 
seconds,  rocking  the  tray  gently. 

They  are  then  dried  in  the  dark.  These  two  baths  are 
sufficient  for  one  dozen  plates,  but  fifteen  drops  of  ammonia 
must  be  added  to  each  bath  after  seven  or  eight  plates  have 
been  treated.  Exposure  through  the  yellow  screen  is  from 
three  to  six  times  that  necessary  with  the  original  emulsion. 

If  the  plates  are  very  rapid,  the  amount  of  ammonia  in  both 
baths  should  be  diminished  one-half. 

For  portraits  the  yellow  screen  is  unnecessary,  unless  blue  or 
red  appear  in  the  draperies. 


156  THE  PHOTOGRAPHIC  NEGATIVE. 

The  addition  of  a  few  drops  of  a  one  to  five  hundred  eosine 
solution  to  the  erythrosine  bath  will  increase  the  sensitiveness 
to  red. 

Prof.  Ehrmann's  Formula. — 

1. — THE  PRELIMINARY  BATH. 

Ammonia 1  dram 

Water 7  ounces 

2.— THE  COLOR  BATH. 

Erythrosine 1J£  drams 

Ammonia 2      drams 

Distilled  water 5%  ounces 

The  plates  are  bathed  as  before. 
VogeVs  Method  with  Azaline*. — Sensitive  to  red. 

Azaline  alcoholic  solution  (1  to  2,500) 340      drops 

Ammonia 34      drops 

Water 22%  drams 

The  plates  are  bathed  for  one  minute  and  then  dried.  A 
yellow  screen  is  used,  and  the  exposure  is  three  or  four  times  as 
long  as  with  wet  plates. 

These  plates  will  keep  from  four  to  six  weeks. 

Obernetter  and  VogeVs  Erythrosine  Bath. — Sensitive  to  yel- 
low; good  for  landscapes  containing  much  green  and  blue. 

Erythrosine,  aqueous  solution  (1  to  1,000) 14     drams 

Silver  solution  (1  to  1,000) 14      drams 

Ammonia 34      drops 

Water 3^  ounces 

The  solution  is  filtered,  and  the  plates  are  bathed  in  it  for 
one  minute,  and  then  dried. 

Exposure  is  made  through  the  yellow  screen. 
The  plates  will  keep  one  week. 
Development  is  effected  in  the  following  : 

1 .     Sulphite  of  soda 3      ounces 

Pyro 3%  drams 

Water 17>£  ounces 

*  According  to  Mallmann  and  Scolik's  analysis,  azaline  is  a  com- 
pound of  chinoline  red  and  chinoline  blue  (cyanine),  500  c.  c.  m.  contain- 
ing one  gramme  of  red  and  one  decigramme  of  blue. 


COLOR-SENSITIVE    PLATES.  157 

2.     Carbonate  of  soda 1J£  ounces 

Water 35      ounces 

Mix  one  volume  of  No.  1  with  two  volumes  of  No.  2. 
Schumann's  Method  with  Cyanine. — 

1. — PRELIMINARY  BATH. 

Water 7  ounces 

Ammonia J^  to  1  dram 

2. — COLOR  BATH. 

Distilled  water 7  ounces 

Alcohol 3  drams 

Ammonia 68  drops 

Alcoholic  solution  of  cyanine  (1  to  500) 3  drams 

Immerse  the  plates  for  two  or  three  minutes  in  No.  1,  and 
then  treat  with  No.  2  for  ninety  seconds. 

Expose  through  the  yellow  screen,  and  develop  with  the 
following : 

1.  Sulphite  of  soda 6      drams 

Sulphuric  acid 8      drops 

Pyro 2      drams 

Water 3J£  ounces 

2.  Carbonate  of  potash 3  drams 

Sulphite  of  soda 6  drams 

Water 7  ounces 

Start  development  with  the  following  weak  developer : 

Solution  No.  1 6  drops 

Solution  No.  2 6  drops 

Bromide  of  potassium  solution  (1  to  10) 1  drop 

Water 2  ounces 

adding  more  pyro,  if  necessary. 

Obernetter*  s  Method  with  Fluoride  of  Silver. — The  plates 
are  washed  with  distilled  water  for  one  minute,  then  drained 
and  covered  one  minute  with  a  solution  of  fluoride  of  silver 
(1  to  2,000).  They  are  next  washed  slightly  under  a  tap,  and 
the  following  solution  flowed  over  them  three  times,  in  differ- 
ent directions : 

Erythrosine  solution  (1  to  1,000) 7  drams 

Azaline  solution  (1  to  2,000) 35  drops 

Carbonate  of  ammonia  solution  (1  to  6) 14  drams 

Water 35  ounces 


158  THE    PHOTOGRAPHIC   NEGATIVE. 

The  plates  are  then  drained  and  dried. 

No  yellow  screen  is  necessary  with  these  plates. 

The  alkaline  pyro  developer  is  to  be  preferred. 

If  the  plates  fog  in  the  developer,  the  usual  bromide  of 
potassium  restrainer  must  be  used. 

Wellington's  Method. — The  plates  are  immersed  for  two 
minutes  in  the  following  bath,  then  rinsed  and  dried : 

Nitrate  of  silver 20  grains 

Carbonate  of  ammonia 90  grains 

Erythrosine  solution  (1  to  500)  10  drams 

Distilled  water 16  ounces 

To  avoid  fog  the  exposed  plates  are  immersed  for  twenty 
seconds  before  development  in  the  following  bath : 

Bromide  of  potassium 120  grains 

Ammonia 4  drams 

Water.    10  ounces 

Then  well  rinsed  and  developed  with  any  good  developer. 

The  use  of  the  yellow  screen  is  unnecessary  if  the  exposures 
are  to  be  made  by  gas  or  lamp-light.  For  day-light  expos- 
ures the  screen  must  be  used  if  the  object  to  be  copied  contains 
much  blue. 

The  interesting  feature  about  the  two  last-mentioned  methods 
is  that  they  seem  to  disprove  the  commonly  accepted  absorp- 
tion theory,  according  to  which  the  function  of  the  various 
dyes  is  to  act  simply  as  optical  sensitizers,  by  increasing  the 
absorption  power  of  the  film  for  certain  colors. 

But  the  fluoride  and  carbonate  of  silver  processes  seem  to 
prove  that  the  orthochromatic  effect  is  due  rather  to  a  chemi- 
cal change,  produced  by  the  presence  of  free  silver  and  a  new 
compound  formed  with  dye. 

The  theory  is  now  meeting  with  general  adoption,  and  it 
makes  the  function  of  the  dye,  in  combination  with  a  sensitive 
silver  haloid,  that  of  a  color-screen  merely,  each  dye  acting 
according  to  its  color  or  shade  of  color. 

The  fact  that  Ducos  du  Hauron  and  Edward  Bierstadt  have 
been  able  to  secure  good  orthochromatic  effects  by  exposing 
ordinary  collodion  or  gelatine  plates  through  variously  colored 


COLOR-SENSITIVE   PLATES.  159 

glasses,  or  cells,  filled  with  colored  liquids,  seems  an  additional 
argument  in  support  of  this  theory. 

Development. — The  use  of  color-sensitive  plates  necessitates 
no  changes  in  the  ordinary  process  of  development,  which  may 
be  effected  with  oxalate  of  iron  or  the  alkaline  developer. 

Great  care  must  be  taken  not  to  expose  the  plates  to  the 
direct  rays  of  the  dark-room  light,  until  development  is  well 
started. 

Schumann  and  Eder  recommend  the  use  of  three  thicknesses 
of  brown  tissue-paper  as  a  safe  medium  through  which  to  filter 
the  light. 

Eder's  Method  of  Developing  Color-Sensitive  Plates. — Dr. 
Eder  prefers  the  oxalate  of  iron  developer,  and  begins  devel- 
opment with  an  old  developer.  A  properly-exposed  plate 
should  show  all  the  details  in  from  five  to  ten  minutes,  but  the 
image  will  probably  be  weak.  In  this  case  it  is  necessary  to 
add  to  the  old  developer  one-half,  or  an  equal  bulk  of  freshly 
mixed  developer,  and  to  prolong  the  development  ten  minutes. 

In  some  cases  the  development  must  be  continued  for  thirty 
minutes.  Slowly  developed  negatives  give  the  best  results. 

Angerer,  Scolik,  Schumann,  Ehrmann,  and  others,  prefer 
the  potash  developer  for  the  development  of  color-sensitive 
plates. 

Captain  Abney  has  recently  made  the  discovery  that  all  that 
is  necessary  to  render  any  plate  color-sensitive  is  to  coat  it 
with  a  solution  of  the  dye  (eosine,  cyanine,  etc.),  in  alcohol  or 
collodion.  The  action  of  light  taking  place  at  the  surface  of 
the  plate,  it  is  said  to  be  sufficient  to  have  the  dye  in  contact 
with  the  surface  molecules  only. 

Coming  from  so  high  an  authority,  the  new  method  is  pre- 
sumably practical;  but  further  knowledge  of  the  results  is 
necessary  before  accepting  it  as  a  rival  of  older  and  well-tried 
methods. 


CHAPTER  XYI. 

BLACK  AND  WHITE  NEGATIVES. 

MOST  of  the  mechanical  printing  processes  require  negatives 
of  greater  density  than  is  necessary  or  desirable  in  negatives 
used  solely  for  printing  upon  sensitized  paper. 

All  the  details  of  lines  or  lettering  must  be  reproduced  with 
perfect  sharpness  in  the  negative,  the  high  lights  being  in- 
tensely black  to  prevent  the  light  from  penetrating  through  on 
to  the  bichromatized  gelatine  plate  beneath.  Such  negatives 
are  technically  known  as  "black  and  white  negatives." 

The  favorite  process  for  the  production  of  this  class  of  work 
has  long  been,  and  still  is,  wet  collodion.  Undoubtedly  it  is 
possible  to  produce  negatives  of  abnormal  density  on  gelatine 
plates,  as  will  be  described  later  in  the  chapter,  but  the  wet 
collodion,  in  the  opinion  of  those  most  skilled  in  this  class  of 
work,  offers  greater  facilities  in  working,  and  produces  better 
and  more  uniform  results. 

The  directions  given  in  the  following  pages  are  based  on 
articles  on  this  subject  which  appeared  in  The  Photographic 
Times. 

Wet  Collodion  Process. — While  any  good  collodion  may  be 
used,  the  following  is  especially  recommended : 

Alcohol 5  ounces 

Ether 5  ounces 

Iodide  of  ammonium 50  grains 

Bromide  of  ammonium 20  grains 

Pyroxyline 50  grains 

The  silver  bath  should  be  acidulated  with  acetic  acid,  which  is 
better  suited  to  vigorous  development,  and  decreases  the  like- 
lihood of  a  foggy  deposit  upon  the  clear  portions  of  the  nega- 
tive. 


BLACK   AND   WHITE   NEGATIVES.  161 

The  plates  are  collodionized  and  sensitized  as  usual. 

The  time  of  exposure  is  a  factor  of  great  importance  in  this 
class  of  work.  If  the  plate  is  under-exposed,  the  lines  will  be 
rough  and  heavy.  If  over-exposed  the  fine  lines  or  stipple  are 
blocked  up.  A  correctly  exposed  plate  shows  the  finest  lines 
only  feebly. 

The  development  should  not  require  longer  than  three  or 
four  minutes,  or  the  negative  will  suffer.  The  following  de- 
veloper gives  good  results : 

Water 16  ounces 

Sulphate  of  iron 1  ounce 

Acetic  acid 1  ounce 

to  which  1  dram  of  sulphate  of  copper  may  be  added  to  give 
more  solidity  to  the  deposit. 

The  negative,  after  development,  should  be  rather  thin,  and 
will  need  to  be  intensified.  The  best  and  safest  method  is  that 
of  Dr.  Eder,  with  nitrate  of  lead. 

The  negative,  after  fixing  and  a  thorough  washing,  is  im- 
mersed in  the  following  bath : 

Nitrate  of  lead 2  ounces 

Red  prussiate  of  potash 3  ounces 

Water 50  ounces 

The  bath  must  be  filtered. 

In  this  bath  the  color  of  the  negative  soon  changes  to  a 
yellowish-white,  which  must  be  allowed  to  deepen  until  the 
proper  degree  of  density  is  reached. 

The  chemical  action  of  this  bath  is  thus  explained.  The 
silver  in  the  image  acts  as  a  reducing  agent,  and  deoxidizes  the 
ferri-cyanide  to  ferro-cyanide,  which  unites  with  the  nitrate  of 
lead  to  form  the  insoluble  ferro-cyanide  of  lead. 

After  being  removed  from  the  lead  bath  the  negative  is 
washed  until  the  drainings  give  no  blue  precipitate  when  the 
sulphate  of  iron  is  added.  It  is  then  blackened  by  immersion 
in  a  1  to  6  solution  of  hydro-sulphate  of  ammonia.  The  ac- 
tion of  this  bath  is  continued  until  the  film  is  black  on  both 
sides.  The  negative  is  then  well  washed,  and  should  show 
great  clearness  in  the  lights,  and  great  density  in  the  ground. 


162  THE   PHOTOGRAPHIC   NEGATIVE. 

If  sufficient  density  was  not  conferred  by  the  lead  bath,  the 
negative  may  be  whitened  in  a  1  to  10  sulphate  of  cadmium 
solution,  then  washed  and  blackened  as  before  with  ammonia, 
which  transforms  lead,  cadmium,  and  silver  into  the  corres- 
ponding sulphides. 

Yellow  fog  or  stains  are  due  to  insufficient  washing  after 
fixing,  but  they  can  be  removed  by  flooding  the  plate  with  a 
sherry-colored  solution  of  iodine  and  iodide  of  potassium,  fol- 
lowed by  fixing  in  a  weak  cyanide  of  potassium  bath. 

Negatives  properly  intensified  with  nitrate  of  lead,  are  won- 
derfully clear  in  the  lines,  of  great  density,  and  produce  fine 
and  high  reliefs  on  bichromatized  gelatine. 

Stripping. — Negatives  intensified  with  lead  are  stripped  by 
coating  the  films  first  with  a  5  grain  solution  of  pure  india- 
rubber  in  benzine,  and  then  with  a  tough  plain  collodion. 
When  dry  the  edges  of  the  film  are  cut  through  to  the  glass, 
and  the  plate  immersed  in  1  to  10  acetic  acid  solution.  The 
film  soon  loosens,  and  may  then  be  detached  from  the  plate. 

Gelatine  Process. — The  great  convenience  attending  the  use 
of  gelatine  emulsion  plates  has  led  to  many  experiments  for 
the  purpose  of  giving  the  negatives  on  gelatine  films  the  quali- 
ties necessary  for  mechanical  printing. 

For  this  purpose  plates  of  a  low  order  of  sensitiveness  are 
correctly  exposed,  and  developed  with  the  oxalate  of  iron  de- 
veloper, to  each  eight  ounces,  of  which  have  been  added  fifty 
drops  of  the  following  solution  : 

Iodine 10  grains 

Iodide  of  potassium 10  grains 

Water  ....   3  ounces 

As  soon  as  the  image  appears,  a  small  quantity  of  the  bro- 
mide of  potassium  restrainer  should  be  added. 

Properly  exposed  plates  thus  developed  will  need  no  intensi- 
fication. 

If  the  negatives  are  not  sufficiently  intense  they  may  be 
strengthened  by  whitening  the  films  in  the  following  bath  : 

Chloride  of  ammonium 16  grains 

Bichloride  of  mercury 1  dram 

Water.  .  24  ounces 


BLACK   AND    WHITE   NEGATIVES. 


163 


The  negatives  are  then  most  thoroughly  washed  and  treated 
with  the  following : 

Cyanide  of  potassium 30  grains 

Iodide  of  potassium 15  grains 

Bichloride  of  mercury 15  grains 

Water 7  ounces 

After  reaching  a  certain  degree  of  density  in  this  bath  the 
reducing  power  of  the  cyanide  begins  to  show  itself,  and  the 
density  is  thus  reduced.  By  taking  advantage  of  this  fact  the 
operator  can  easily  determine  the  character  of  the  negative. 


CHAPTER  XYIL 

INSTANTANEOUS  PHOTOGRAPHY. 

THE  time  of  exposure  necessary  to  imprint  a  developable 
image  on  the  sensitive  surface,  has  been  reduced  to  the  one 
twenty-six-hundredth  part  of  a  second,  and  even  lower,  under 
exceptionally  favorable  circumstances. 

This  great  increase  in  sensitiveness  has  opened  a  new  and 
delightful  field  to  the  photographer,  making  it  possible  for 
him  to  give  graphic  delineations  to  fleeting  effects  of  motion, 
expression,  and  grouping,  which  but  lately  were  impossible  of 
exact  and  accurate  delineation. 

The  detective  camera  has  become  a  necessary  part  of  the 
photographic  outfit,  and  the  tourist  who  is  provided  with  one 
of  these  modern  instruments,  finds  little  difficulty  in  securing 
interesting  studies  of  the  lands  and  peoples  visited  by  him. 

But  instantaneous  photography,  with  detective  cameras  and 
highly  sensitive  plates,  is  not  so  certain  as  the  more  common 
method  of  longer  exposures  on  slower  plates. 

If  the  development  of  a  correctly-timed  exposure  is  a  deli- 
cate operation,  much  more  delicate  is  it  to  coax  a  good  print- 
ing image  from  a  plate  which  has  received  an  exposure  of 
only  a  fraction  of  a  second. 

It  is,  however,  but  a  transfer  of  difficulties  and  perplexities 
from  one  stage  of  the  process  to  another.  In  the  case  of  a 
timed  exposure  the  operator's  judgment  is  most  exercised  to 
determine  the  length  of  exposure  best  suited  to  the  view  be- 
fore him. 

"With  instantaneous  exposures,  however,  it  is  in  development 
that  good  judgment  is  most  needed  to  make  the  most  possible 
out  of  the  plate. 

He  who  would  be  successful  in  instantaneous  work  must 


INSTANTANEOUS  PHOTOGRAPHY.  165 

have  a  thorough  knowledge  of  the  plate  used,  the  distance  and 
illumination  of  the  object,  and  the  conditions  of  development. 

It  is  taken  for  granted  that  the  plates  used  have  at  least  as 
high  a  sensitometer  number  as  25,  which  is  rapid  enough  for 
most  purposes,  and  even  in  the  detective  camera  they  are 
more  often  over  than  under-exposed,  owing  to  the  use  of  a 
diaphragm  with  too  large  an  opening. 

The  distance  and  illumination  of  the  object  determine  the 
amount  of  light  to  be  admitted,  and,  consequently,  the  size  of 
the  diaphragm  and  the  speed  of  the  shutter. 

Objects  near  at  hand  require  the  admission  of  more  light 
than  those  at  a  distance,  because  their  actinic  force  is  dis- 
tributed over  a  larger  area  of  sensitive  surface. 

If  the  illumination  is  from  behind  the  camera,  a  smaller 
diaphragm  may  be  employed  than  when  the  shadows  fall 
transversely  across  the  field. 

Objects  in  shadow  will  require  a  larger  diaphragm  than 
those  fully  illuminated. 

In  general  it  may  be  said  that  the  best  effects,  both  as 
regards  definition  and  tone,  are  secured  by  using  a  medium- 
sized  diaphragm  and  increasing  or  diminishing  the  speed  of 
the  shutter. 

The  following  table  is  given  as  the  results  of  the  author's 
experiments  with  a  Morrison  lens  of  8-inch  focus,  using  No. 
25  plates. 

For  brightly-illuminated  landscapes,  with  rapid  shutter,  use 
diaphragm  opening  T^-. 

For  seascapes,  with  quick  shutter,  use  ^. 

For  figures,  animals,  etc.,  in  the  foreground,  use  T£,  with 
moderate  speed. 

For  thick  foregrounds,  with  foliage  in  the  middle  distance, 
use  full  opening,  with  fair  speed  of  shutter,  or,  for  better 
definition,  y^-,  with  slower  shutter. 

For  buildings  and  confined  scenes  generally,  when  well 
illuminated,  use  T^-,.with  moderate  speed. 

These  may  be  taken  as  standard  measurements,  and  the 
resulting  exposures,  if  properly  developed,  will  yield  negatives 
with  sufficient  pluck  to  print  well. 


166  THE   PHOTOGRAPHIC  NEGATIVE. 

Development. — Instantaneously  exposed  plates  should  be 
developed  slowly,  using  a  developer  weak  in  pyro  and  alkali, 
and  the  plate  should  be  protected  from  the  action  of  the  light. 

The  following  method  is  given,  not  as  the  best  or  only  pos- 
sible one,  but  as  the  one  which  has  given  the  author  uniformly 
good  results. 

The  developer  is  compounded  as  follows : 
No.  1. 

Pyro 1  ounce 

Sulphite  of  soda 1  ounce 

Sulphuric  acid 10  drops 

Water 10  ounces 

Dissolve  the  soda  first,  then  the  pyro,  and  then  add  the  sul- 
phuric acid. 

No.  2. 

Carbonate  of  potash 1  ounce 

Sulphite  of  soda f 1  ounce 

Water 10  ounces 

One  dram  of  each  of  these  solutions  contains  six  grains  of 
pyro,  sulphite  and  carbonate. 
To  develop.— Take 

Water 4  ounces 

Solution  No.  1 1  dram 

Solution  No.  2 1  dram 

Immerse  the  plate  in  this  and  cover  the  tray  with  an  opaque 
screen.  If  after  two  or  three  minutes  the  high  lights  do  not 
appear,  add  half  a  dram  of  No.  2.  As  much  as  four  drams  of 
No.  2  can  be  added  without  producing  fog,  but  in  most  cases 
two  to  three  drams  will  be  found  sufficient. 

As  soon  as  the  details  are  well  out,  add  one  dram  of  No.  1, 
and  continue  the  development  until  the  image  is  visible  at  the 
back  of  the  plate.  Instantaneous  exposures  seem  to  lose  more 
density  in  the  fixing-bath  than  timed  exposures,  therefore  they 
should  be  developed  further. 

If,  after  the  addition  of  two  drams  of  No.  2,  the  details  still 
hang  back,  do  not  seek  to  hasten  matters  by  the  addition  of 
more  alkali,  but  dilute  the  developer  one-half  with  water,  or 


INSTANTANEOUS  PHOTOGRAPHY.  167 

remove  the  plate  from  the  tray  and  immerse  in  a  weak  alka- 
line solution  (one  dram  of  No.  2  to  four  ounces  of  water)  until 
the  details  appear,  then  return  to  the  developer  to  which  the 
second  dram  of  No.  1  has  been  added. 

It  will  generally  be  advisable  to  give  the  plates  a  prelimin- 
ary soaking  for  two  or  three  minutes  in  the  weak  alkaline 
solution,  given  above,  before  applying  the  developer.  This 
method  is  valuable  in  the  case  of  heavy  foliage  and  dark 
shadows. 

If  the  image  flashes  up  immediately,  add  a  few  drops  of  a 
ten  per  cent,  solution  of  bromide  of  potassium. 

The  following  method  of  developing  instantaneous  expos- 
ures with  Beach's  formula,  given  on  page  121,  is  taken  from 
the  Photographic  Times. 

"Take  of  solution  No.  1,  or  pyro,  45  or  50  minims,  and 
mix  with  3  fluid  ounces  of  water,  not  too  cold — about  60  deg. 
in  summer  and  70  deg.  in  winter  is  most  satisfactory.  Add 
30  minims  of  the  No.  2,  or  potash,  solution,  and  flood  the 
plate  without  previous  soaking  in  water.  Have  at  hand,  in 
soak  in  a  basin  of  clean  running  water,  a  wide  camel's-hair 
brush,  such  as  is  commonly  sold  for  dusting  off  plates,  and 
with  it  lightly  brush  the  surface  of  the  plate  under  the  liquid, 
to  prevent  air-bells  and  pin-holes.  The  picture  will  come  up 
slowly  and  steadily,  and  should  be  pushed  to  considerable  den- 
sity, until  the  outlines  begin  to  "  sink  in."  When  the  plate  is 
held  up  to  the  red  light,  the  dark  parts  should  be  of  an  opaque, 
velvety  black,  and  a  dim,  but  clear,  ruddy  glow  ought  to  shine 
through  the  lighter  details.  Looked  at  on  the  wrong  side,  the 
image  should  be  discernible.  It  is  safer  to  press  the  develop- 
ment a  trifle  too  far  than  to  halt  too  soon,  for  it  is  always  easy 
to  reduce  an  over-developed  plate  ,  but  in  practice  there  is  not 
much  likelihood  of  over-intensity  in  a  well-timed  instantaneous 
plate,  for  it  loses  density  prodigiously  in  fixing.  Wash  well 
before  fixing,  and  when  the  whiteness  goes  off,  transfer  to  a 
cool  bath  of  fresh  hyposulphite,  and  let  it  soak  for  a  few 
minutes  longer. 

It  sometimes  happens  that,  even  with  this  weak  developer, 
the  image  conies  up  too  rapidly,  giving  full  details  while  den- 


168  THE  PHOTOGRAPHIC  NEGATIVE. 

sity  lags.  In  such  cases,  add  half  a  dram  more  of  the  pyro- 
gallol  mixture  and  ten  or  fifteen  drops  of  the  following 
solution : 

Water 4  ounces 

Sodium  sulphite 1  ounce  (437  grains) 

Sodium  carbonate  (chem.  pure,  dry) 1  ounce  (437  grains) 

Ammonium  bromide 20  grains 

On  the  other  hand,  if  the  image  shows  undesirable  contrast 
and  backwardness  in  the  details,  the  developer  should  be  fur- 
ther diluted  with  an  ounce  of  water,  and  ten,  or  even  twenty, 
drops  of  the  standard  No.  2  (potash)  solution  added." 

The  careful  study  of  these  two  methods  will  enable  the 
intelligent  operator  to  employ  any  alkaline  developer  for  the 
development  of  instantaneous  exposures. 


CHAPTEE  XVIII. 

TOUCHING  UP  THE  NEGATIVE. 

NEGATIVES  are  rarely  perfect  in  every  respect  when  fin- 
ished. There  is  often  a  want  of  harmony,  frequently  an  over- 
abundance of  pin-holes.  These  and  various  other  defects 
necessitate  judicious  doctoring  before  good  prints  can  be  ob- 
tained. 

Avoiding  any  discussion  concerning  the  retouching  of  por- 
trait negatives  as  too  difficult  and  serious  a  matter  to  be  ade- 
quately treated  in  a  general  work  like  the  present,  a  few 
methods  of  improving  poor  negatives  and  remedying  the 
defects  of  faulty  ones  will  be  briefly  indicated  in  the  present 
chapter. 

A  very  common  fault,  in  landscape  negatives,  is  a  want  of 
harmonious  blending  of  the  tones;  the  high  lights  are  too 
dense,  the  shadows  too  thin.  Such  a  negative,  if  printed  from 
without  any  touching  up,  would  give  very  unsatisfactory 
prints. 

The  shadows  must  be  brought  up  to  the  proper  density  to 
print  well  with  the  high  lights. 

A  common  method  of  securing  this  end  is  to  paste  tissue  or 
tracing  paper  over  the  back  of  the  negative,  cutting  out 
the  high  lights  with  a  sharp  penknife.  In  this  way  the  den- 
sity of  the  shadows  is  increased  ;  the  effect  may  be  hightened 
by  applying  black  lead  with  a  stump  to  the  parts  which  re- 
quire it. 

Another  very  efficient  means  of  securing  better  gradation, . 
is  to  coat  the  back  of  the  plate  with  a  plain  collodion,  to  which 
a  tinge  of  red  or  yellow  has  been  given  by  the  addition  of 
aniline  dyes.  This  method  is  particularly  good  for  strength- 
ing  weak  negatives,  as  any  desired  depth  of  color  may  be 


170  THE   PHOTOGRAPHIC   NEGATIVE. 

given   to   the  collodion    by   increasing  the   amount  of  dye 
added. 

The  author  much  prefers,  to  either  of  these  methods,  the  use 
of  the  mat  varnish,  the  formula  for  which  is  as  follows  : 

One  dram  of  powdered  sandarac  is  dissolved  in  fourteen 
drams  ;of  ether,  fifteen  grains  of  Canada  balsam,  and  five  or 
six  grains  of  pure  benzine  or  benzole  are  then  added  and  the 
varnish  filtered.  It  is  applied  by  flowing  it  over  the  back  of 
the  negative,  which  is  not  warmed.  If  one  coating  does  not 
give  sufficient  density  two  or  three  may  be  given. 

The  advantage  of  this  varnish  is  that  it  may  be  removed 
from  the  denser  portions  of  the  negative  with  a  brush  dipped 
in  mastic  varnish,  and  that  it  admits  of  any  amount  of  re- 
touching with  plumbago  and  the  stump,  or  with  the  pencil. 

If  desired,  the  varnish  may  be  colored  with  aniline  dye. 

Pinholes,  scratches,  and  other  defects  of  a  similar  nature, 
should  be  touched  up  with  India  ink  applied  with  a  very  fine 
brush.  The  ink  should  be  used  nearly  dry  and  laid  on  thinly, 
to  attain,  as  far  as  possible,  the  density  of  the  surrounding 
parts. 

Local  reduction  of  density  may  be  effected  by  rubbing  the 
over-dense  portions  with  a  piece  of  fine  linen  drawn  over  the 
finger  end  and  moistened  with  alcohol,  or  by  mixing  a  small 
quantity  of  any  of  the  reducing  agents,  given  on  page  128. 
with  gum  water,  and  applying  the  mixture  with  a  brush. 

Local  intensification  may  be  produced  in  the  same  way. 

These  general  hints  are  sufficient  to  enable  the  skillful 
operator  to  improve  the  printing  quality  of  defective  nega- 
tives, which  is  their  only  aim. 


CHAPTER  XIX. 

PHOTO-MICROGRAPHY. 

PHOTOGRAPHY  has  proved  a  most  useful  handmaid  to  micro- 
scopy, and  the  photographic  camera  has,  to  a  large  extent, 
emancipated  the  microscopist  from  the  camera  lucida.  Vari- 
ous methods  have  been  devised  for  the  photographic  reproduc- 
tion of  the  highly  magnified  images  given  by  the  microscope, 
some  of  the  best  of  which  have  been  selected  for  description. 

Mercer's  Plwto-j&Licrograpliic  Camera. — This  instrument 
is  so  well  illustrated  in  Fig.  30  as  to  require  but  little  further 
explanation.  It  is  light  and  portable,  and  can  be  used  with  the 
microscope  in  any  position.  It  is  used  in  connection  with  the 
eye-piece,  and  carries  plates  measuring  2|  by  3^  inches. 

Its  essential  parts  consist  of  a  small  box,  to  which  is  at- 
tached a  brass  cone  provided  with  a  draw  tube  for  insertion 
into  the  body  of  the  microscope.  The  weight  rests  upon  the 
brass  arm,  as  shown,  none  of  it  being  upon  the  sliding  parts. 
Coarse  adjustment  is  made  by  sliding  the  instrument  up  and 
down  on  the  arm;  the  fine  adjustment  is  given  by  the  micro- 
meter screw  of  the  microscope. 

This  little  instrument,  while  not  well  adapted  for  serious 
scientific  work,  is  well  suited  to  the  wants  of  the  amateur,  on 
account  of  the  small  cost,  its  simplicity,  and  the  rapidity  of  its 
manipulation. 

The  Scomll  Photo-Micrographic  Camera. — Fig.  31  illus- 
trates another  simple  form  of  the  micrographic  camera,  using 
plates  4£  by  5£  inches. 

It  consists  of  an  ordinary  bellows  camera,  having  a  cone  ex- 
tension in  front  to  give  the  additional  length  of  focus  neces- 
sary to  give  the  desired  amplification  to  the  image. 

To  this  cone  the  body  of  the  microscrope,  inclined  horizon- 


172 


THE    PHOTOGRAPHIC   NEGATIVE. 


FlG.  31. 


PHOTO-MICROGKAPHY.  173 

tally,  is  adapted  by  means  of  a  black  velvet  sleeve.  The 
source  of  illumination  shown  in  the  cut  is  Carbutt's  multum 
in  parvo  lantern,  with  the  condensers  in  place.  Any  other 
method  of  illumination  may  be  substituted. 

AtwoocPs  Photo-Micrographic  Camera — Fig.  32  illustrates 
a  very  convenient  form  of  apparatus  which  dispenses  with  the 
microscope  body.  The  coarse  adjustment  is  effected  by  slid- 
ing the  stage  upon  the  solid  base.  The  sub-stage  bar  is  on  the 
plane  of  the  stage,  and  is  provided  with  an  adjustable  and 
centering  sub-stage  to  hold  any  accessories  desired.  The  fine 
adjustment  is  in  the  nose  piece,  a  brass  tube  with  society 
screw  to  receive  any  ordinary  microscopic  objective.  The 
focusing  is  done  by  means  of  a  rod  passing  under  the  box  to 
the  back  and  terminating  in  a  milled  head  as  shown.  The 
illumination  is  from  a  lamp  from  behind  the  stage. 

Amplifiers  are  provided  to  increase  the  size  of  the  image 
thrown  on  the  ground-glass  screen.  The  whole  apparatus  is 
mounted  upon  a  cherry  board  of  convenient  length. 


FIG.  32. 

The  form  shown  in  the  cut  allows  the  use  of  plates  4  by  5 
inches  and  under,  but  a  modification  has  been  introduced, 
with  bellows  extension,  which  increases  the  size  of  the  image 
to  the  whole  plate.  Either  form  may  be  fitted  with  mirrors, 
stereoscopic  and  other  attachments  required  by  the  varying 
needs  of  the  investigator. 

Walmsley's  Photo-Micrographic  Camera. — Figs.  33  and 
34  illustrate  the  very  complete  and  ingenious  apparatus,  de- 
vised by  Mr.  W.  H.  Walmsley,  and  manufactured  by  the 
American  Optical  Company. 


174 


THE    PHOTOGRAPHIC    NEGATIVE. 


Fig.  33  illustrates  the  original  and  cheaper  form,  adapted 
only  to  the  making  of  negatives  up  to  the  half-plate  size.    » 


FIG.  33. 


Fig.  34  shows  the  latest  form  by  which  the  original  appara- 
tus is  converted  into  a  small  enlarging,  reducing,  and  copying 


FIG.  34. 


The  following  description  of  the  complete  camera,  first  pub- 
lished in  the  Photographic  Times,  is  also  applicable  to  the 


PHOTOMICROGRAPHY.  175 

cheaper  form,  excepting  that  the  latter  cannot  be  used  for  en- 
larging, reducing,  or  copying.  In  all  other  particulars  the 
two  boxes  are  identical. 

"  The  camera  box  (of  mahogany)  is  square,  carrying  a  Flam- 
mang  single  plate-holder  for  4^  by  5^  plates ;  usable  vertically 
or  horizontally,  and  with  kits  for  3^  by  4J  plates.  The  bel- 
lows are  in  two  sections,  with  a  central  division  of  mahogany, 
which  carries  a  removable  partition,  to  which  a  suitable  recti- 
linear photographic  lens  can  be  attached,  for  enlarging,  re- 
ducing, or  copying.  A  light-tight  door  on  one  side  of  this 
wooden  section  gives  ready  access  to  the  lens  for  inserting  or 
removing  diaphragms,  or  other  necessary  manipulations,  whilst 
a  milled  head,  accessible  from  the  same  opening,  clamps  the 
lens-bearing  section  firmly  to  the  bed  of  the  camera  at  any 
desired  point. 

"  The  bellows  have  an  extension  of  two  feet  in  addition  to 
the  length  of  the  box,  sliding  very  smoothly  upon  Y-shaped 
ways,  which,  for  greater  convenience,  are  made  in  two  sections, 
firmly  attached  to  each  other  by  wooden  dowels  and  a  solid 
brass  screw,  worked  by  a  milled  head. 

"The  bellows  are  firmly  held  at  any  desired  point  of  exten- 
sion by  a  cam,  operated  bysa  lever  conveniently  placed  at  the 
rear  of  the  focusing  screen,  which  latter  is  hinged  at  the  bot- 
tom, and,  when  not  in  use,  lies  out  of  the  way  upon  the  exten- 
sion bed.  The  screen  itself  is  of  the  very  finest  ground-glass, 
but  is  used  only  for  arranging  the  portion  of  the  object  to  be 
photographed  properly  in  the  center  of  the  plate,  as  no  sur- 
face can  be  ground  finely  enough  to  permit  the  sharp  focusing 
of  any  delicately-lined  object.  For  this  purpose,  a  circle  or 
disc  of  thin  microscopic  covering-glass  is  attached  with  bal- 
sam to  the  center  of  the  ground-glass  screen,  which  clears 
away  all  the  inequalities  of  the  latter,  and  leaves  an  exquisitely 
fine  surface  to  receive  the  image,  which,  by  using  an  ordinary 
focusing  glass,  may  be  as  sharply  defined  as  in  the  eye-piece  of 
the  microscope. 

"  The  front  of  the  camera  (which  is  double-shifting,  for  the 
purpose  of  centering)  carries  a  cone-shaped  tube,  which  re- 
ceives the  tube  of  the  microscope  when  the  latter  is  inclined 


1Y6  THE   PHOTOGRAPHIC   NEGATIVE. 

to  a  horizontal  position,  and  conveys  the  image-bearing  rays 
of  the  light  therefrom  into  the  body  of  the  camera.  This 
cone  is  removable,  and  in  its  place  may  be  inserted  kits,  carry- 
ing negatives  from  quarter  to  half  size  for  enlargement,  or  re- 
duction to  lantern  slides,  as  may  be  desired.  Or  a  front  board, 
bearing  a  lens,  may  be  inserted  in  its  place,  converting  the 
camera  into  a  copying  one.  Indeed,  a  more  complete  instru- 
ment for  all  the  purposes  for  which  it  was  devised  could 
scarcely  be  conceived  or  desired.  Its  design  was  the  result  of 
several  years'  work  and  experiment  on  the  part  of  Mr.  Walms- 
ley  ;  and  the  Scovill  Manufacturing  Company  have  carried  out 
his  plans  in  their  usual  masterly  manner,  leaving  nothing  to 
be  desired. 

"  In  use,  the  camera  is  attached  to  a  solid  platform  (which 
also  carries  the  microscope  and  lamp)  by  a  screw,  such  as  is 
used  with  an  ordinary  tripod.  By  this  means  any  jar  or  tre- 
mor, produced  by  a  passing  vehicle  or  other  means,  is  com- 
municated to  microscope  and  camera  alike,  preventing  any 
diminution  of  sharpness  in  the  negative.  By  this  arrange- 
ment, also,  the  whole  apparatus  is  so  compact  that,  with  the 
bellows  closed,-  the  operator  can  easily  see  the  image  upon  the 
ground  glass,  and  at  the  same  time  reach  the  milled  heads  upon 
the  microscope  controlling  the  stage  and  focusing  movements, 
permitting  the  arrangement  of  the  subject  with  the  greatest 
nicety.  But,  when  the  bellows  are  extended  to  their  full 
length,  some  appliance  becomes  necessary  to  operate  the  fine 
adjustment  of  focus,  whilst  the  eye  can  discern  the  changes 
upon  the  screen.  This  is  most  simply  effected  by  Mr.  Wahns- 
ley,  in  the  employment  of  a  fine  cord  passing  in  a  groove 
around  the  periphery  of  the  milled  head  of  the  fine  adjust- 
ment screw,  and  thence  through  a  series  of  hook-eyes  to  the 
rear  of  the  camera  bed,  where  it  is  held  taut  by  a  couple  of 
leaden  weights.  The  slightest  pull  upon  either  cord  moves 
the  fine  adjustment  screw  with  the  utmost  nicety." 

Nothing  more  complete  or  convenient  than  this  apparatus 
can  well  be  devised.  By  its  use  no  difficulty  will  be  experi- 
enced in  securing  by  lamp-light  photo-micrographs  of  all  trans- 
parent objects  requiring  microscopical  examination.  Opaque 


PHOTO-MICROGRAPHY. 


m 


bodies  may  be  photographed  by  illuminating  them  by  sun- 
light reflected  from  a  mirror. 

White's  Pttoto-Micrographic  Apparatus. — Fig.  35  is  an 


FIG.  35. 

illustration  of  a  novel  piece  of  apparatus,  which  dispenses  with 
the  use  of  the  microscope,  and  projects  a  magnified  image  of 
the  object  upon  a  movable  screen.  It  is  the  invention  of  Mr. 
T.  Charters  White,  of  England,  who  claims  for  it  the  follow- 
ing advantages  :  That  the  field  of  view  is  only  limited  by  the 
size  of  plate  employed  ;  that  a  great  range  of  amplification  is 
possible,  and  the  ease  with  which  all  the  adjustments  are  made. 

The  following  description  of  the  construction  and  method  of 
working  is  condensed  from  that  given  by  Mr.  White  in  the 
"  British  Journal  Almanac,  for  1887." 

A  narrow,  lidless  box  is  fastened  by  screws  to  one  end  of 
a  baseboard,  two  inches  in  thickness,  and  two  and  a  half  feet 
in  length.  The  other  end  of  the  baseboard  is  provided  with  a 
groove,  in  which  slides  the  wooden  bar  which  carries  the  f  rame 
which  holds  the  focusing  screen  and  sensitive  plates.  An  or- 
dinary printing  frame  answers  well  for  this  purpose.  An  ob- 
long opening  is  cut  in  the  top  of  the  box  over  which  a  metal 
chimney  is  fitted. 

In  the  end  of  the  box,  facing  the  plate-holder,  a  square 
opening  is  cut  and  closed  with  a  brass  plate  tapped  with  the 
standard  screw  gauge,  thus  allowing  the  use  of  any  standard 


178 


THE    PHOTOGRAPHIC   NEGATIVE. 


objective.  The  movable  stage  support  is  fastened  to  the  end 
of  the  box,  below  the  brass  plate,  the  stage  being  moved  to 
and  from  the  objective  by  a  long  micrometer  screw.  The 
front  of  the  box  is  covered  with  a  black  velvet  curtain. 

Two  focusing  screens  are  used ;  one,  for  coarse  adjustment, 
is  made  by  gumming  a  sheet  of  smooth  white  paper  on  a  glass 
plate.  This  is  placed  in  the  holder,  and  the  object  roughly  ar- 
ranged and  focused.  The  screen  is  then  removed,  and  a  piece 
of  plain  glass  substituted  for  it,  having  fine  lines,  drawn  close 
together  with  a  writing  diamond,  on  the  surface  which  faces 
the  object.  These  lines  are  brought  into  the  focus  of  a  focus- 
ing glass,  placed  against  the  back  of  the  glass,  and  the  stage 
moved  back  and  forth  until  the  details  of  the  object  are  seen 
with  equal  sharpness.  The  glass  is  then  removed  and  the  sen- 
sitive plate  substituted  for  it. 

This  apparatus  presents  some  novel  features,  and  seems  well 
adapted  to  the  photographing  of  transparent  objects.  Of 
course  all  white  light  must  be  excluded  from  the  room  while 
the  sensitive  plate  is  in  position,  save  that  which  comes 
through  the  objective. 

Apparatus  for  the  Vertical  Microscope. — It  is  sometimes 
necessary,  or  desirable  to  retain  the 
microscope  in  the  vertical  position. 
Such  an  arrangement  is  shown  in  Fig. 
36,  the  microscope  being  omitted  as 
unnecessary  to  the  clearness  of  the 
description. 

A  A,  are  slotted  bars  supporting  the 
camera  body,  B,  with  its  bellows. 
There  are  three  of  these  bars  fastened 
firmly  to  a  slab  of  hard- wood,  as  shown 
in  the  cut.  The  box,  B,  carries  the 
ground  glass  frame,  D,  at  its  upper 
end,  and  is  provided  with  a  door,  C,  in 
one  side.  The  object  of  this  door  is  to 
admit  of  focusing,  without  mounting 
FIG.  36.  a  step-ladder.  It  must  fit  light-tight. 

The  microscope  is  adapted  to  the  cone  in  the  base  of  the  in- 
strument by  means  of  a  velvet  sleeve. 


PHOTOMICEOGRAPHT.  179 

There  are  many  other  ways  of  securing  photographic  repre- 
sentations of  the  images  seen  in  the  microscope,  but  they  are 
all  modifications  of  the  various  arrangements  just  described, 
which  are  believed  to  be  sufficiently  varied  to  meet  all  possible 
needs. 

It  is  now  proposed  to  enter  somewhat  fully  into  the  practical 
manipulations  of  photo-micrography,  and  to  give  some  hints 
on  the  choice  of  the  microscope  and  objectives. 

The  Microscope. — Any  standard  form  of  microscope,  bin- 
ocular or  monocular,  may  be  employed  ;  the  body  should  be 
capable  of  being  included  to  the  horizontal  position.  The 
best  form  for  photo-micrography  is  one  with  a  broad  short 
tube,  because  the  field  of  illumination  is  then  less  restricted 
than  when  a  long  tube  is  employed.  If  the  binocular  stand 
be  used,  the  prism  must  be  withdrawn  sufficiently  to  allow  all 
the  light  to  pass  through  the  straight  tube. 

The  eye-piece  may  be  used,  or  not,  as  the  operator  prefers. 
If  it  is  not  used,  the  tube  must  be  lined  witli  some  soft  dark 
material,  to  prevent  reflections  which  cause  spectral  spots 
called  "  ghosts,"  in  the  negatives. 

A  mechanical  stage,  revolving  in  the  optical  axis  of  the  mi- 
croscope, a  sub-stage  revolving  in  the  plane  of  the  stage,  a  con- 
denser, and  a  double  or  triple  nose-piece  will  be  found  neces- 
sary for  serious  work. 

The  latter  is  especially  necessary  when  working  with  high 
powers,  as  an  object  can  be  quickly  brought  into  proper  posi- 
tion under  a  low  power,  and  the  high  power  substituted  by  re- 
volving the  nose-piece. 

The  Objectives. — The  experimenter  is  recommended  to  be- 
gin with  the  low  powers,  and  to  attempt  higher  powers  only 
after  he  has  gained  complete  mastery  over  the  manipulations 
with  the  low  powers.  The  one-half  inch  objective  is  a  very 
good  power  to  begin  with,  and  the  one-eighth  inch  is  about 
as  high  as  can  be  worked  in  photo-micrography,  although  much 
depends  upon  the  skill  of  the  operator. 

When  working  by  artificial  light  with  low  powers,  no  diffi- 
culty will  commonly  be  experienced  through  want  of  coinci- 
dence between  the  chemical  and  visual  foci.  With  higher 


180  THE   PHOTOGRAPHIC   NEGATIVE. 

powers,  however,  it  is  necessary  to  determine  the  difference 
by  actual  experiment  and  allowed  for  it  in  focusing,  or 
specially  corrected  objectives,  may  be  employed.  The  photo- 
micrographic  series  of  the  Bausch  Lomb  Company,  of  Roches- 
ter, are  free  from  this  defect,  besides  giving  a  very  flat  field 
and  fine  definition. 

Source  of  Light. — The  object  to  be  photographed  may  lie 
illuminated  by  sunlight  or  artificial  light,  the  latter  being  pre- 
ferred on  account  of  its  greater  certainty  and  uniformity. 
Any  good  microscopic  lamp,  burning  oil,  will  answer  well  for 
photo-micrographic  work,  and  a  little  practice  will  enable  the 
operator  to  make  such  simple  arrangements  as  may  be  neces- 
sary to  secure  the  best  results.  The  usual  practice  is  to  place 
the  lamp  behind  the  object  and  in  line  with  it.  Some  opera- 
tors, however,  prefer  to  illuminate  the  object  by  means  of 
light  reflected  from  a  white  screen  placed  behind  the  stage. 

With  objectives  of  low  powers,  condensers  will  not  be 
needed ;  they  must,  however,  be  used  when  working  with  the 
higher  powers,  which  require  the  most  careful  adjustments 
and  the  most  scrupulous  attention  to  minute  details,  and  which 
are,  therefore,  not  recommended  except  to  the  most  advanced 
manipulators. 

If  lamps  with  flat  wicks  are  used,  the  flame  must  be  placed 
at  an  angle  to  the  plane  of  the  stage,  in  order  to  avoid  the 
dark  spot  in  the  center  of  the  field.  Even  illumination  of  the 
object  must  be  secured  by  the  use  of  the  diaphragms  with 
which  the  stage  should  be  provided. 

The  author  believes  that  the  incandescent  electric  light  is 
superior  to  the  oil  lamp,  as  it  occupies  less  space,  gives  out  no 
heat,  and  can  be  adapted  to  the  revolving  sub-stage  bar.  A 
very  efficient  light  of  this  kind  is  manufactured  by  the  Bausch 
&  Lomb  Company. 

Measuring  the  Magnification. — The  scientific  value  of  a 
photo-micrographic  print  is  greatly  increased  if  its  exact  mag- 
nification is  indicated. 

This  is  easily  effected  by  placing  upon  the  stage  a  microme- 
ter ruled  in  -rta  and  Wmi  of  an  inch,  and  focussing  its  image  upon 
the  ground-glass.  The  exact  value  of  each  division  is  then 
readily  determined. 


fHOTOMICROGRAPHY.  "     l8l 

To  avoid  the  necessity  of  making  this  measurement  each  time 
an  object  is  to  be  photographed,  it  is  well  to  make  the  measure- 
ments at  various  points  in  the  extension  of  the  bellows,  and  to 
mark  those  points  with  their  exact  power  of  magnification. 

The  Sensitive  Plates. — The  nature  of  the  work  to  be  done 
will  determine  the  kind  of  plate  to  be  employed.  For  micro- 
metric  purposes,  where  the  greatest  precision  is  absolutely  neces- 
sary, collodion  films  are  to  be  preferred  to  gelatine  films,  be- 
cause their  distortion  is  less,  being  not  more  than  2  or  3  in 
1000  parts,  while  gelatine  films  often  show  an  error  of  1  in  100 
parts. 

For  studying  details,  however,  gelatine  is  vastly  superior  to 
collodion.  The  method  of  preparation  must  have  been  such 
as  to  combine  extreme  sensitiveness  with  density  and  strong 
contrasts.  Abney  states  that  the  best  plates  for  this  class  of 
work  are  those  prepared  with  iodide  of  silver,  by  boiling,  and 
without  the  use  of  ammonia. 

For  colored  objects  the  use  of  color-sensitive  plates  in  con- 
nection with  the  yellow  screen  is  strongly  advised. 

Plates  coated  with  Davanne's  emulsion,  given  on  page  102, 
are  well  adapted  to  photo-micrographic  work. 

Focusing. — For  arranging  the  object  in  the  field,  and  for 
the  preliminary  focusing  the  ground-glass  is  used.  For  the 
final  focusing  the  ground-glass  is  replaced  by  a  plain  glass,  on 
whose  inner  surface  a  series  of  fine  parallel  lines  have  been 
drawn  with  a  writing  diamond.  The  focus  of  a  focusing-glass 
placed  against  the  back  of  the  glass  plate  is  adjusted  to  render 
these  lines  sharp  and  distinct.  The  image  is  then  brought  into 
focus,  and  the  exposure  made. 

Exposure. — The  time  of  exposure  varies  according  to  the 
nature  and  color  of  the  objects,  the  power  of  the  objective,  and 
the  nature  of  the  illumination.  Mr.  Walmsley  gives  the  fol- 
lowing table  for  the  different  powers  with  the  oil  lamp : 

l-J-  inch 3    to  45    seconds 

1    inch 5    to  60    seconds 

finch i  to    1£  minutes 

^jinch i  to    3    minutes 

£  inch 2    to    7    minutes 

inch. 5    to  10    minutes 


182 


THE    PHOTOGKAPHIC   NEGATIVE. 


These  figures,  however,  are  only  approximate,  and  the  oper- 
ator must  learn  from  experience  here  as  in  other  departments 
of  photography. 

Development. — Any  form  of  developer  may  be  used,  either 
the  oxalate  of  iron  or  the  alkaline.  It  is  best  to  develop  more 
for  detail  than  for  density,  resorting  to  intensification,  if  neces- 
sary, to  bring  the  negative  up  to  the  proper  printing  density. 


CHAPTER  XX. 


MICRO-PHOTOGRAPHY. 

THE  term  micro-photography  has  been  applied  to  the  pro- 
duction, on  a  scale  of  microscopic  fineness,  of  positives  on 
glass  from  large  negatives.  These  positives  are  subsequently 
mounted  at  one  extremity  of  a  Stanhope  lens  of  great  magni- 
fying powers  and  enclosed  in  many  ways  in  tiny  opera-glasses, 
keys,  penholders,  medallions,  etc.,  and  sold  as  curiosities. 

The  process  by  which  these  microscopic  pictures  are  pro- 
duced is  little  known  and  rarely  practised.  To  the  best  of  the 
writer's  knowledge,  there  is  but  one  producer  of  these  articles 
in  America,  and  his  methods  are  not  known  to  the  author. 

The  method  here  given  is  that  employed  by  the  best  French 
producers  of  micro-positives,  and  is  described  in  all  its  details 
to  enable  the  experimenter  to  produce  good  results. 

A  negative  is  first  made,  on  a  whole  plate,  of  the  object  to  be 
reproduced.  This  negative  should  not  be  made  over-dense, 

A as  it  is  to  be  used  in  the 

copying  camera  for  the  re- 
production of  the  reduced 
positives.  It  is  not  to  be 
varnished,  but  when  dry  it 
is  copied  by  any  method 
known  to  the  operator,  the 
usual  copying  lens  being  re- 
placed by  a  brass  plate  carry- 
ing from  twenty-five  to  fifty 
very  small  objectives,  as 
_  shown  in  Fig.  37,  which 
Fig  37  shows  only  a  few  of  the 

objectives. 

This  apparatus  is  known  as  the  microscopic  apparatus,  and 
can  be  obtained  of  most  large  dealers  in  photographic  goods. 


184:  THE   PHOTOGRAPHIC   NEGATIVE. 

It  will  give  fifty  reduced  positives  on  a  2x2£  inch  plate.  There- 
fore, by  using  a  4x5  plate,  and  a  holder  adapted  for  making 
two  exposures  on  one  plate,  one  hundred  impressions  may  be 
taken  without  changing  the  plate. 

A  piece  of  ground-glass  is  placed  behind  the  negative  to  be 
copied,  which  is  accurately  focused  on  the  ground-glass  at  the 
back  of  the  copying  camera,  using  for  this  purpose  a  powerful 
focusing  glass. 

The  exposure  is  made  as  usual,  and  the  plates  developed  in 
the  customary  manner. 

Since,  owing  to  the  small  size  of  the  image,  it  is  manifestly 
impossible  to  watch  the  progress  of  development  very  closely, 
a  few  trial  exposures  must  be  made,  developed,  and  fixed,  that 
the  operator  may  acquire  a  knowledge  of  the  proper  duration 
of  the  exposure,  the  correct  strength  of  the  developer,  and  the 
time  of  development. 

After  development,  the  plates  are  fixed,  washed,  and  dried, 
and  then  varnished  with  the  following  varnish : 

Benzoin 220  grains. 

Alcohol 3^  ounces. 

They  are  then  laid  face  down  on  a  clean  sheet  of  white 
paper,  and  cut  in  parallel  lines  with  a  diamond  between  the 
positives,  which  are  then  separated  from  each  other,  after 
which  they  are  mounted. 

Mounting. — For  this  purpose  a  table  with  a  sheet-iron  top  is 
needed.  The  edges  of  the  top  are  turned  up  to  form  a  tray, 
which  is  filled  with  fine  sand,  over  which  is  spread  a  piece  of 
thick  black  cloth,  on  which  are  placed  the  Stanhopes  and  the 
positives,  with  the  side  bearing  the  images  uppermost. 

The  sand  is  kept  warm  by  means  of  a  spirit  or  oil-lamp.  A 
jar  of  Canada  balsam,  previously  warmed,  a  pair  of  small  brass 
pliers,  and  a  small,  flat  stick  of  wood  are  also  placed  within 
convenient  reach. 

One  of  the  lenses  is, taken  with  the  right  hand  between  the 
pliers,  and  a  small  quantity  of  the  balsam  applied  to  its  flat 
end,  which  is  then  placed  upon  one  of  the  small  images,  after 
which  it  is  set  aside  to  cool.  When  cool,  the  edges  of  the 


MICKO-PHOTOGRAPHY. 


185 


positives  are  rounded  off  on  a  grindstone,  and  then  covered  as 
desired. 

Wet  collodion  plates  are  best  suited  for  this  purpose,  owing 
to  the  liability  of  gelatine  film  sustaining  some  damage  when 
the  plates  are  cut  down. 

Although  these  micro-positives  are  chiefly  used  as  curious 
ornaments,  they  have  a  more  serious  value,  as  affording  means 
for  the  storage  in  small  space  of  reduced  copies  of  valuable 
originals,  and  for  the  reproduction  of  reduced  maps,  charts, 
etc  ,  for  the  tourist's  use. 


CHAPTER  XXI. 

THE  TRANSFORMATION  OF  NEGATIVES  INTO  POSITIVES. 

MANY  heliographic  processes  require  a  positive  for  the 
production  of  the  printing  plate,  as  does  also  the  production 
of  enlarged  negatives.  Many  methods  have  from  time  to  time 
been  proposed  to  obviate  the  necessity  of  taking  a  positive  di- 
rect from  the  negative  by  contact  printing  or  by  exposure  in 
the  copying  camera. 

Methods  have  also  been  worked  out  for  producing  positives 
direct  in  the  camera,  but  all  these  methods  have  proved  too 
uncertain  to  come  into  general  use. 

M.  E-oux,  a  skilful  French  manipulator,  has  worked  out  a 
practical  process  for  the  chemical  transformation  of  negatives 
into  positives,  which  should  prove  valuable  to  the  process 
worker. 

All  essential  details  of  the  process  are  given  in  the  present 
chapter. 

No.  1. — Collodion  for  Drawings  and  Engravings. 

PLAIN  COLLODION. 

a.  Ether 21 J^  ounces. 

Alcohol 10%  ounces 

Pyroxyline 150  grains 

IODIZER. 

b.  Alcohol 2%  ounces 

Iodide  of  potassium 123  grains 

Iodide  of  cadmium 30  grains 

Iodine 0.7  grains 

Chloride  of  zinc 30  grains 

%.— Collodion  for  Half-tones. 

PLAIN  COLLODION. 

a.  Same  as  above. 

IODIZER. 

b.  Alcohol 3^4  ounces 

Iodide  of  cadmium 92  grains 

Iodide  of  ammonium 30  grains 

Iodide  of  zinc 30  grains 

Bromide  of  cadmium 22  grains 

Bromide  of  ammonium 22  grains 

Chloride  of  zinc 80  grains 


THE  TRANSFORMATION  OF  NEGATIVES  INTO  POSITIVES.        187 

THE  SENSITIZING  BATH. 

Distilled  water 85  ounces 

Nitrate  of  silver 1234  grains 

Acetic  acid 1%  ounces 

The  plates  are  sensitized  as  usual,  and  dried  moderately. 

Exposure. — For  negatives  which  are  to  be  transformed,  the 
exposure  should  be  a  trifle  longer  than  would  be  necessary  for 
an  ordinary  negative. 

Development. — The  following  developer  is  recommended  by 
M.  Koux: 

Water 35  ounces 

Sulphate  of  iron 770  grains 

Acetic  acid l^j  ounces 

Alcohol IJg  ounces 

Nitric  acid 30  drops 

Ammonia 30  drops 

The  best  method  of  preparing  the  developer  is  to  pulverize 
the  sulphate,  then  to  add  the  nitric  acid,  and,  after  stirring, 
the  ammonia.  The  iron  turns  black,  and  stifling  fumes  are 
given  off.  As  soon  as  these  cease,  the  water  is  added,  and, 
finally,  the  alcohol  and  the  acetic  acid. 

Negatives  developed  in  this  bath  are  strong  and  brilliant, 
with  good  printing  density.  For  the  present  purpose,  how- 
ever, it  is  necessary  to  intensify  them  slightly,  after  washing 
off  the  developer,  with  the  following : 

Water 35  ounces 

Pyrogallic  acid 77  grains 

Citric  acid 385  grains 

Alcohol 3  drams 

to  a  sufficient  quantity  of  which  are  added,  when  wanted  for 
use,  a  few  drops  of  the  following : 

Distilled  wnter 35  ounces 

Nitrate  of  silver 308  grains 

Acetic  acid If  ounces 

After  intensification,  the  negative  is  washed  slightly,  but  not 
sufficiently  to  remove  all  the  free  nitrate,  a  slight  excess  of 
which  is  useful  in  determining  the  formation  of  the  positive 
image  during  the  latter  exposure  to  diffused  light. 

The  Transformation  of  the  Negative. — Two  operations  are 
necessary  to  transform  the  negative  into  a  positive : 


188  THE    PHOTOGRAPHIC   NEGATIVE. 

1.  Exposure  of  the  unfixed  negative  to  diffused  light. 

2.  Destruction  of  the  negative  image  by  dissolving  the  re- 
duced silver,  and  development  of  the  positive  image. 

1. — Exposure  to  Diffused  Light. — The  unfixed  negative  is 
placed,  face  up,  on  a  piece  of  black  cloth,  and  exposed  to  weak 
diffused  light  until  the  positive  image  viewed  by  the  reflected 
light  is  clearly  seen  with  a  bluish-black  tone  on  the  grey 
ground  of  the  silver  of  the  negative  image.  The  time  neces- 
sary to  produce  this  effect  will  vary  from  a  few  seconds  to  two 
or  three  minutes,  according  to  the  strength  of  the  light. 

The  color  of  the  positive  image  is  due  to  the  presence  of  a 
small  quantity  of  chloride  of  silver. 

2. — Destruction  of  the  Negative  Image,  and  Development  of 
the  Positive. — If  re-development  followed  immediately  upon 
the  exposure  to  diffused  light,  the  two  images  would  be  con- 
fused together.  Hence  it  is  first  necessary  to  destroy  the 
negative  image.  This  is  done  by  placing  the  plate,  after  wash- 
ing slightly,  in  the  following  solution  : 

Water 25  ounces 

Bichromate  of  potash 460  grains 

Nitric  acid lOf  ounces 

The  plate  is  immersed  in  this  bath  until  the  reduced  silver 
of  the  negative  image  is  entirely  dissolved  ;  that  is,  until  the 
film  assumes  a  yellow  color,  except  in  the  lines  of  the  positive, 
which  will  strike  a  slightly  reddish  tint,  owing  to  the  forma- 
tion of  chromate  of  silver. 

The  plate  is  then  washed  until  all  traces  of  the  acid  are 
removed. 

The  positive  image  is  then  developed  by  pouring  over  the 
plate  sufficient  of  the  following : 

Water 35  ounces 

Pyrogallic  acid :   385  grains 

Citric  acid 308  grains 

Alcohol 1£  ounces. 

This  solution  is  allowed  to  remain  on  the  plate  for  a  few 
seconds ;  it  is  then  poured  off  into  a  graduate  containing  a  few 
drops  of  aceto-nitrate  of  silver  solution,  given  above,  and  the 
mixture  poured  back  on  the  plate. 


THE  TRANSFORMATION  OF  NEGATIVES  INTO  POSITIVES.        189 

The  positive  image  will  now  gradually  develop  with  a 
strength  proportioned  to  the  amount  of  silver  added  to  the 
developer.  Reproductions  of  line-work  require  a  strong  and 
rapid  development  in  order  to  preserve  the  fineness  of  the 
lines  and  perfect  transparency  of  the  ground.  Reproductions 
of  portraits,  landscapes,  and  paintings  require  slow  develop- 
ment with  little  silver  to  preserve  the  gradations  of  the  half- 
tones. 

Fixing. — The  developed  positive  is  fixed  as  usual,  reproduc- 
tions of  line-work,  preferably  in  a  1  to  50  solution  of  cyanide 
of  potassium  ;  those  in  which  it  is  desired  to  preserve  the  half- 
tones, in  the  usual  hypo  solution. 

Intensification. — The  positive,  if  too  thin,  may  be  intensified 
either  with  the  usual  pyro  and  silver  intensifier  or  with  bi- 
chloride of  mercury. 

Success  with  this  method  depends  on  the  quality  of  the 
negative  and  the  complete  washing  away,  after  the  exposure 
to  diffused  light,  of  all  the  free  silver. 

Reversed  negatives  obtained  by  exposure  through  the  glass 
are,  after  development  and  drying  the  backs,  exposed  to  dif- 
fused light  through  the  glass  in  the  plate-holder. 

Without  this  precaution  there  is  danger  of  fog,  unless  all 
the  iodide  of  silver  acted  upon  by  light  was  reduced  by  the 
developer  and  the  intensifier. 


CHAPTEK  XXII. 

OBERNETTER'S     METHOD     FOR     THE     DIRECT     PRODUCTION    OF    NEGATIVES 
FROM    NEGATIVES. 

IN  the  "  American  Annual  of  Photography  for  1887,"  the 
late  E.  Obernetter  described  a  practical  method  for  the  repro- 
duction of  negatives  in  any  size. 

In  the  issue  of  the  "Annual  for  1888,"  Herr  F.  Mueller 
gives  a  few  valuable  notes  on  the  process. 

Both  of  these  papers  have  been  freely  drawn  upon  in  the 
following  description,  which  has  been  written  only  after  a 
thorough  trial  of  the  method,  which  has  demonstrated  its 
practical  utility.  This  test  of  the  process  was  the  more  severe, 
since  the  negatives  thus  reproduced  were  in  many  cases  very 
far  from  possessing  that  high  degree  of  technical  excellence 
which  is  to  be  desired  in  negatives  which  are  reproduced. 

The  first  requisite  to  complete  success  is  faultless  negatives 
of  moderate  density.  The  next  is  that  the  plates  on  which 
the  reproduced  negatives  are  made  be  thinly  but  evenly  coated 
with  an  emulsion  containing  a  comparatively  small  percentage 
of  gelatine. 

Evenness  of  coating  is  greatly  assisted  by  using  plate  or 
patent  plate  glass. 

The  negative  to  be  reproduced  is  placed  in  the  copying 
camera,  with  the  film  side  turned  away  from  the  lens,  and 
focused  to  the  desired  dimensions,  and  the  sensitive  plate 
exposed  for  a  considerably  longer  time  than  would  be  neces- 
sary for  the  production  of  a  good  positive,  and  developed  with 
the  usual  oxalate  of  iron  developer  till  the  positive  image  is 
distinctly  visible  at  the  back  of  the  plate. 

If  the  exposure  was  sufficiently  prolonged,  the  image  flashes 
up  at  once,  the  plate  blackens  quickly,  and  the  development  is 
completed  withinjtwo  minutes. 


DIRECT  PRODUCTION  OF  NEGATIVES  FORM  NEGATIVES.        191 

It  is  important  that  both  sides  of  the  plate  appear  black, 
with  only  faint  indications  of  the  high  lights.  Unless  this  is 
the  case  the  reproduced  negative  will  fail  to  give  the  fine 
details  and  gradations  of  the  original. 

When  fully  developed,  the  plate  is  well  washed,  and  then 
immersed  in  the  following  chromic  solution  till  the  black 
deposit  has  completely  changed  to  white : 

Water 35      ounces 

Bichromate  of  potassium 1540      grains 

Nitric  acid  (c.  p.) 17)^  ounces 

For  use,  the  solution  is  diluted  with  water  in  the  proportion 
of  1  to  15. 

Three  or  four  minutes'  immersion  in  this  bath  will  be  re- 
quired to  produce  a  thorough  change  of  color. 

When  the  change  is  complete,  the  plate  is  thoroughly 
washed,  and  then  made  sensitive  by  pouring  over  it  repeat- 
edly, and  flowing,  from  corner  to  corner,  the  following  solu- 
tion: 

Water 35  ounces 

Ammonia 6  drams 

Bromide  of  ammonium 308  grains 

The  plate  is  again  washed,  and  exposed  to  diffused  daylight 
for  a  length  of  time  varying  from  one  to  six  seconds,  according 
to  the  sensitiveness  of  the  plate  and  the  intensity  of  the  light. 

After  this  second  exposure,  the  plate  is  re-developed  with 
the  developer  used  for  the  first  development. 

The  negative  will  develop  slowly  with  every  appearance  of 
being  under-exposed.  But  if  the  second  exposure  was  suffi- 
ciently prolonged  density  will  gradually  increase  to  the  desired 
degree.  If,  however,  the  time  of  exposure  was  too  short,  the 
negative  will  refuse  to  gain  in  strength. 

The  plate  is  fixed  in  the  usual  hypo  solution,  well  washed, 
treated  with  dilute  hydrochloric  acid  to  clear  up  the  shadows, 
and  finally  washed  again  to  remove  all  traces  of  the  acid. 


INDEX. 


Preface   3 

List  of  Authorities 5 

GENERAL    REMARKS    ON  SENSITIVE 
SURFACES,  ETC. 

Substances  Sensitive  to  Light. .     7 

The  Film 7 

The  Dark-room  and  Laboratory  10 

The  Drying-box 12 

Utensils 16 

Solutions 18 

Filtration 18 

Precipitation 20 

Washing  Precipitates 20 

Decantation 20 

Distilling  Apparatus 21 

PRELIMINARY   REMARKS  ON  EXPOS- 
URE, DEVELOPMENT,  ETC. 

Exposure 23 

Physical  Conditions  Governing 

the  Exposure 24 

Chemical    Conditions   Govern- 
ing the  Exposure 24 

Optical    Conditions  Governing 

the  Exposure 25 

Development 25 

Fixing 28 

Washing 29 

Intensification 30 

Reduction 30 

Varnishing 31 

CALOTYPE  PROCESS,  THE. 

Fox  Talbot's  Process. 

Sensitizing  Solutions 32 

Exposure 33 


Development 34 

Fixing 34 

Waxing 34 

Le  Gray's  Process. 

Waxing 35 

Iodide  Bath 35 

Sensitizing.. . .    .  36 

Exposure 37 

Development 37 

Pelegry's  Process. 

Sensitizing 87 

Tannin  Bath 37 

Exposure 38 

Development 38 

SENSITIVE  SURFACES  ON  GLASS. 

Preparation  of  the  Glass. 

Cleaning  Bath  for  Old  Collo- 
dion Films 39 

The  Final  Cleaning  of  the  Glass 
for  the  Albumen  and  Collo- 
dion Process 39 

Albumenizing  the  Glass 40 

Treatment  of  the    Glass  for  the 

Gelatine  Process. 

Cleaning  the  Glass 41 

Polishing  with  Talc 41 

Substrata 41 

ALBUMEN  PROCESS,  THE. 

General  Remarks  44 

Gobert's  Method. 

Formulae 45 

Cleaning  the  Glass 45 

Coating 46 


194 


INDEX. 


Drying  the  Plates 46 

Fuming  with  Iodine 47 

Sensitizing 47 

Development 47 

Fixing 47 

Sella's  Modification 48 

Bagot's  Modification 48 

Couppier's  Modification 49 

Whipple  and  Black's  Albumen 
Honey  Process 49 

COLLODION  PROCESS,  WET  PLATES, 
THE. 

General  Remarks 50 

Preparation  of  Pyroxyline 51 

The  Solvents 52 

Thelodizers 72 

Plain  Collodion 53 

Salted  Collodion 53 

Bromized  Collodion 54 

Iodized  Collodion 54 

Bromo-iodized  Collodion 54 

Carbutt's   Collodion 45 

Vogel's  Collodion 55 

Equivalent  Collodion 55 

Care  of  the  Collodion 55 

Filtering  Collodion 56 

The  Sensitizing  Bath 56 

Management  of  the  Bath 58 

Testing    the    Strength    of    the 

Bath 59 

Development 60 

Intensification 60 

Fixing 61 

Practical  Manipulations. 

Sensitizing  in  the  Vertical  Bath  62 

Sensitizing  in  Trays 62 

Exposure 62 

Development 63 

Intensification 64 

Fixing 64 

Varnishing 64 

Defects ..  64 


COLLODION  PROCESS,  DRY  PLATES, 
THE. 

General  Remarks 65 

Taupinot'sCollodio-albumen  Pro- 
cess. 

Manipulations 66 

Exposure  and  Development. . .  67 

Boivin's  Process. 

Manipulations 68 

Sensitizing 69 

Development 70 

The  Tannin   Process. 

The  Collodion 71 

The  Preservative 71 

Development 71 

Sutton's  Process 71 

The  Gum-gallic  Process 72 

COLLODION    EMULSION,    COLLODIO- 
BROMIDE  OF  SILVER. 

General  Remarks 73 

The  Pyroxyline 73 

The  Bromides 74 

Making    the     Collodion      and 

Emulsion 74 

Ripening  the  Emulsion 75 

Washing  and  Organifying 75 

Chardon's  Method. 

The  Collodion 76 

Emulsifying  76 

Re-emulsification 77 

Cooper's  Process. 

The  Collodion 78 

The  Emulsion 78 

The  Substratum 78 

The  Preservative 79 


ItfDEX. 


195 


Abney's  Collodio-bromide  Emul- 
sion. 

Plain  Collodion 79 

Bromide  Solution 79 

Albumen  Solution 79 

Emulsification ...   80 

Abney's  Collodio-chloride  Emul- 
sion. 

Emulsification 80 

The   Preservative 81 

The  Developer 81 

The  Toning-bath 81 

Canon  Beechey's  Process. 

The  Bromized  Solution 82 

The  Collodion 82 

The  Sensitizer 82 

Development 83 

DevelopersforCollodion  Emul- 
sion Plates 83 

Intensification 84 

Defects 84 

GELATINE  PROCESS,  THE 

General  Remarks. ..  ..86 


Preparation  of  Gelatine  Emulsions. 

General  Observations 87 

Theory  of  the  Method 87 

Choice  of  Soluble  Bromides. ..   88 
Tables  for  Emulsions,  Calcula- 
tions   89 

Choice    and   Treatment  of   the 

Gelatine 91 

Proportion  of  the  Ingredients..  92 

Emulsifying 93 

Silvering 96 

Digesting 97 

Breaking-up  and  Washing. ...  97 

Draining 98 

Re-melting 98 


Formulae  for  Emulsions. 

Andra's 98 

Henderson's  Ammonia  Method  99 
Eder's  Ammonio-nitrate  of  Sil- 
ver Method 99 

Braun's  Method 100 

Scolik's     Ammonio-nitrate     of 

Silver  Method 101 

Scolik's  Modification  of  Hender- 
son's Cold  Emulsion  Method.  101 

Davanne's  Method 102 

Burton's  Precipitation  Method.  103 

Fabre's  Method 103 

Burton's  Slow  Emulsion 105 

Gelatine-Chloride  Emulsion  for 

Slides  and  Transparencies. .  .106 
Wellington's      Citro  -  Chloride 

Emulsion  for  Opals 106 

Sczekely's    Process    with    Car- 
bonate of  Silver. ..  ..107 


COLLODIO-GELATINE   EMULSIONS  : 

Dr.  Vogel's 108 

Kosarzewenski's 109 

COATING  THE  PLATES  : 

The  Levelling  Shelf 110 

Button's  Cooling  Tank 110 

Coating  Tripod 110 

Coating  Board 112 

Coating  Box 113 

Other  Methods  of  Coating 113 

Quantity  of  Emulsion  Necessary 
to    Cover   Various    Sizes    of 

Plates: 114 

Drying 114 

Packing  the  Plates 114 

DEVELOPMENT,  FIXING,  ETC.: 
Development — 

General  Remarks 115 

Oxalate  of  Iron  Developer.    ...116 


196 


ISfDEX, 


Alkaline  Development — 

General  Remarks. 118 

Density 120 

The  Quantity  of  Pyro  and  Alkali 
to  be  Used 120 

Formulae — 

Cooper's 121 

Beach's 121 

The  Author's  122 

Carbutt's 123 

Edward's 124 

Henderson's 124 

E.  Van  Sothen's 124 

Dr.  Martell's 124 

Notes  on  the  General  Composition 
of  Developers — 

TheOxalateof  Iron  Developer.  124 

Alkaline  Developers 124 

The  Hydrochinone  Developer.  .125 

The  Alum  Bath 125 

Fixing 125 

Washing 125 

Test  for  Hypo 126 

Bellitzki's  Hypo-Eliminator 126 

Intensifying :     Formulae — 

Eder's 126 

Thompson's 127 

Wallace  and  Bartletfs 127 

Uranium  Intensifier 127 

Reduction — 

Farmer's  Reducer 128 

Bellitzki's  Reducer 128 

Varnishing 128 

PAPER  NEGATIVES,  STRIPPING  FILMS 
ON  PAPER,  CARD-BOARD,  AND 
COLLODION  : 

The  Paper 130 

Sizing  the  Paper 131 


PAGE 

Coating  the  Paper 131 

Balagny's  Method 133 

Stripping  Films,  Paper  Support — 

Chenneviere's  Method 134 

Balagny's  Method 135 

Fabre's  Method 135 

Milson's  Method 138 

Eastman's  Method 138 

Stripping   Films  on  Cardboard 

Supports 136 

Balagny's  Method  with  Methyl- 
alcohol 136 

Coating  Board 137 

Pellicular  Films  Without  Sup- 
port     138 

Mefhods  of  Exposing  Films  on 

Paper  Supports 139 

Development 140 

Drying 142 

Oiling 143 

Retouching 143 

Printing 143 

Preserving  Paper  Negatives  . .  .143 

Stripping— 

Eastman's  Method 143 

Chenneviere's 145 

Fabre's 145 

Failures   in    the    Gelatino-Bro- 
mide  Process 147 

METHODS  OF  STRIPPING  FILMS  FROM 
GLASS  PLATES  : 

Collodion  Films 151 

Gelatine  Films 152 

COLOR-SENSITIVE  PLATES  : 

General  Remarks 153 

The  Light-Screen 154 

Color-Sensitive  Gelatine  Emul- 
sion  155 

Color-Sensitive  Bath  Plates 155 


INDEX. 


19T 


PAGE 

Scolik's  Method  with   Erythro- 

sine 155 

Ehrmann's  Method 156 

Vogel's  Method,  with  Azaline.  .156 
Obernetter  and     Vogel's    Ery- 

throsine  Bath 156 

Schumann's   Method   with   Cy- 

anine 157 

Obernetter's  Method  with  Fluor- 
ide of  Silver 157 

Wellington's  Method 158 

Development 159 

Abuey's  Method  of  Making  Dry- 
plates  Color-sensitive 159 

BLACK  AND  WHITE  NEGATIVES. 

General  Remarks 160 

The  Wet  Collodion  Process. 

The  Collodion 160 

The  Silver  Bath 160 

The  Exposure 161 

The  Developer 162 

The  Intensifier 162 

Stripping 162 

The  Gelatine  Process. 

The  Developer 162 

The  Intensifier  162 

INSTANTANEOUS  PHOTOGRAPHY. 

General  Remarks 164 

Development. 

The  Author's  Method 166 

Beach's  Method 167 

Touching-up  the  Negative 169 

PHOTO-MICROGRAPHY. 

Mercer's  Photo-Micrographic 
Camera 171 

The  Scovill  Photo-Micrographic 
Camera...  171 


PAGE 

Atwood's     Photo-Micrographic 

Camera 173 

Walmsley's  Photo-Micrographic 

Camera 174 

White's     Photo-Micrographic 

Apparatus. 177 

Apparatus  for  the  Vertical  Mi- 
croscope  178 

The  Microscope 179 

The  Objectives 179 

The  Source  of  Light 180 

Measuring  the  Magnification. .  .180 

The  Sensitive  Plates 181 

Focussing 181 

Exposure 182 

Development   182 


MICRO-PHOTOGRAPHY. 

General  Description  of  the  Pro- 
cess  183 

Mounting 184 


THE  TRANSFORMATION  OF  NEGATIVES 
INTO  POSITIVES. 

Roux's  Process. 

The  Collodion 186 

Development 187 

The  Transformation  of  the  Neg- 

tive 187 

Exposure  to  Diffused  Light 188 

Distinction  of  the  Negative  Im- 
age  188 

Development    of    the    Positive 

Image 188 

Fixing 189 

Intensification 189 

Obernetter's  Method  for  the  Di- 
rect production  of  Negatives 
from  Negatives 190 


198 


INDEX. 


LIST  OF  CUTS. 


Number.  PAGE 

1.  Plan  of  Dark-room 11 

2.  Ventilation  of  Dark-room...  12 

3.  Davanne's  Drying-box 13 

4.  Davanne's  Drying-rack 14 

5-9.  Scolik's  Drying-box 15 

10.  Draining-rack 17 

11.  Apparatus  for  Making  Solu- 

tions    18 

12-13.  Apparatus  for  Hot  Filtration  19 

14.  Washing  Bottle 20 

15.  Vever's  Distilling  Apparatus  21 

16.  Collodion  Filter 56 

17.  Silvering  Apparatus 76 

18.  David  and  Scolik's  Emulsify- 

ing Apparatus 93 

19.  Davanne's   Emulsifying  Ap- 

paratus   94 

20.  Spraying  Apparatus 96 

21.  Abney's  Washing  Apparatus  97 


22.  Levelling  Screw  Ill 

23.  Burton's  Cooling  Tank Ill 

24.  Coating  Tripod Ill 

25.  Coating  Board Ill 

26.  Coating  Box 113 

28.  Apparatus  for  Coating  Paper.  132 

29.  Coating  Board 137 

30.  Mercer's  Photo-Micrographic 

Apparatus 172 

31.  Scovill's  Photo-Micrographic 

Apparatus 172 

32-33.  W  a  1  m  s  1  e  y's  Photo-Micro- 
graphic Apparatus 174 

34.  White's  Photo-Micrographic 

Apparatus 177 

35.  Apparatus    for  the   Vertical 

Microscope 178 

36.  Arrangement  of  Lenses    for 

Micro-Photography. 183 


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